String.IndexOf String.IndexOf String.IndexOf String.IndexOf Method

Definizione

Restituisce l'indice in base zero della prima occorrenza di un carattere Unicode specificato o di una stringa all'interno di questa istanza.Reports the zero-based index of the first occurrence of a specified Unicode character or string within this instance. Il metodo restituisce -1 se la stringa o il carattere non viene trovato nell'istanza.The method returns -1 if the character or string is not found in this instance.

Overload

IndexOf(String, Int32, StringComparison) IndexOf(String, Int32, StringComparison) IndexOf(String, Int32, StringComparison) IndexOf(String, Int32, StringComparison)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata nell'oggetto String corrente.Reports the zero-based index of the first occurrence of the specified string in the current String object. I parametri specificano la posizione iniziale della ricerca nella stringa corrente e il tipo di ricerca da usare per la stringa specificata.Parameters specify the starting search position in the current string and the type of search to use for the specified string.

IndexOf(String, Int32, Int32) IndexOf(String, Int32, Int32) IndexOf(String, Int32, Int32) IndexOf(String, Int32, Int32)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata in questa istanza.Reports the zero-based index of the first occurrence of the specified string in this instance. La ricerca viene eseguita iniziando dalla posizione specificata dei caratteri ed esamina un determinato numero di posizioni.The search starts at a specified character position and examines a specified number of character positions.

IndexOf(Char, Int32, Int32) IndexOf(Char, Int32, Int32) IndexOf(Char, Int32, Int32) IndexOf(Char, Int32, Int32)

Restituisce l'indice in base zero della prima occorrenza del carattere specificato in questa istanza.Reports the zero-based index of the first occurrence of the specified character in this instance. La ricerca viene eseguita iniziando dalla posizione specificata dei caratteri ed esamina un determinato numero di posizioni.The search starts at a specified character position and examines a specified number of character positions.

IndexOf(String, StringComparison) IndexOf(String, StringComparison) IndexOf(String, StringComparison) IndexOf(String, StringComparison)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata nell'oggetto String corrente.Reports the zero-based index of the first occurrence of the specified string in the current String object. Un parametro specifica il tipo di ricerca da usare per la stringa specificata.A parameter specifies the type of search to use for the specified string.

IndexOf(String, Int32, Int32, StringComparison) IndexOf(String, Int32, Int32, StringComparison) IndexOf(String, Int32, Int32, StringComparison) IndexOf(String, Int32, Int32, StringComparison)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata nell'oggetto String corrente.Reports the zero-based index of the first occurrence of the specified string in the current String object. I parametri specificano la posizione di ricerca iniziale nella stringa corrente, il numero di caratteri nella stringa corrente in cui eseguire la ricerca e il tipo di ricerca da usare per la stringa specificata.Parameters specify the starting search position in the current string, the number of characters in the current string to search, and the type of search to use for the specified string.

IndexOf(Char, StringComparison) IndexOf(Char, StringComparison) IndexOf(Char, StringComparison) IndexOf(Char, StringComparison)

Restituisce l'indice in base zero della prima occorrenza del carattere Unicode specificato in questa stringa.Reports the zero-based index of the first occurrence of the specified Unicode character in this string. Un parametro specifica il tipo di ricerca da usare per il carattere specificato.A parameter specifies the type of search to use for the specified character.

IndexOf(Char, Int32) IndexOf(Char, Int32) IndexOf(Char, Int32) IndexOf(Char, Int32)

Restituisce l'indice in base zero della prima occorrenza del carattere Unicode specificato in questa stringa.Reports the zero-based index of the first occurrence of the specified Unicode character in this string. La ricerca ha inizio alla posizione del carattere specificata.The search starts at a specified character position.

IndexOf(String) IndexOf(String) IndexOf(String) IndexOf(String)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata in questa istanza.Reports the zero-based index of the first occurrence of the specified string in this instance.

IndexOf(Char) IndexOf(Char) IndexOf(Char) IndexOf(Char)

Restituisce l'indice in base zero della prima occorrenza del carattere Unicode specificato in questa stringa.Reports the zero-based index of the first occurrence of the specified Unicode character in this string.

IndexOf(String, Int32) IndexOf(String, Int32) IndexOf(String, Int32) IndexOf(String, Int32)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata in questa istanza.Reports the zero-based index of the first occurrence of the specified string in this instance. La ricerca ha inizio alla posizione del carattere specificata.The search starts at a specified character position.

IndexOf(String, Int32, StringComparison) IndexOf(String, Int32, StringComparison) IndexOf(String, Int32, StringComparison) IndexOf(String, Int32, StringComparison)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata nell'oggetto String corrente.Reports the zero-based index of the first occurrence of the specified string in the current String object. I parametri specificano la posizione iniziale della ricerca nella stringa corrente e il tipo di ricerca da usare per la stringa specificata.Parameters specify the starting search position in the current string and the type of search to use for the specified string.

public:
 int IndexOf(System::String ^ value, int startIndex, StringComparison comparisonType);
public int IndexOf (string value, int startIndex, StringComparison comparisonType);
member this.IndexOf : string * int * StringComparison -> int
Public Function IndexOf (value As String, startIndex As Integer, comparisonType As StringComparison) As Integer

Parametri

value
String String String String

Stringa da cercare.The string to seek.

startIndex
Int32 Int32 Int32 Int32

Posizione iniziale della ricerca.The search starting position.

comparisonType
StringComparison StringComparison StringComparison StringComparison

Uno dei valori di enumerazione che specifica le regole di ricerca.One of the enumeration values that specifies the rules for the search.

Restituisce

Posizione dell'indice in base zero del parametro value dall'inizio dell'istanza corrente se la stringa viene trovata oppure -1 in caso contrario.The zero-based index position of the value parameter from the start of the current instance if that string is found, or -1 if it is not. Se value è Empty, il valore restituito è startIndex.If value is Empty, the return value is startIndex.

Eccezioni

startIndex è minore di 0 (zero) o maggiore della lunghezza della stringa.is less than 0 (zero) or greater than the length of this string.

comparisonType non è un valore StringComparison valido.is not a valid StringComparison value.

Esempi

L'esempio seguente illustra tre overload del IndexOf metodo di cui trovare la prima occorrenza di una stringa all'interno di un'altra stringa utilizzando i diversi valori del StringComparison enumerazione.The following example demonstrates three overloads of the IndexOf method that find the first occurrence of a string within another string using different values of the StringComparison enumeration.

// This code example demonstrates the 
// System.String.IndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the first occurrence of a character using different " + 
                   "values of StringComparison.";
    string resultFmt = "Comparison: {0,-28} Location: {1,3}";

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string CapitalAWithRing = "\u00c5"; 

// Define a string to search. 
// The result of combining the characters LATIN SMALL LETTER A and COMBINING 
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
    string cat = "A Cheshire c" + "\u0061\u030a" + "t";

    int loc = 0;
    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

// Clear the screen and display an introduction.
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because culture affects the result. For example, 
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Console.WriteLine("The current culture is \"{0}\" - {1}.", 
                       Thread.CurrentThread.CurrentCulture.Name,
                       Thread.CurrentThread.CurrentCulture.DisplayName);

// Display the string to search for and the string to search.
    Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"", 
                       CapitalAWithRing, cat);
    Console.WriteLine();

// Note that in each of the following searches, we look for 
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
// the string was not found.
// Search using different values of StringComparison. Specify the start 
// index and count. 

    Console.WriteLine("Part 1: Start index and count are specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparison. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, 0, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparison. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }
    }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the first occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/
' This code example demonstrates the 
' System.String.IndexOf(String, ..., StringComparison) methods.

Imports System
Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the first occurrence of a character using different " & _
                              "values of StringComparison."
        Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
        
        ' Define a string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim CapitalAWithRing As String = "Å"
        
        ' Define a string to search. 
        ' The result of combining the characters LATIN SMALL LETTER A and COMBINING 
        ' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
        ' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
        Dim cat As String = "A Cheshire c" & "å" & "t"
        
        Dim loc As Integer = 0
        Dim scValues As StringComparison() =  { _
                        StringComparison.CurrentCulture, _
                        StringComparison.CurrentCultureIgnoreCase, _
                        StringComparison.InvariantCulture, _
                        StringComparison.InvariantCultureIgnoreCase, _
                        StringComparison.Ordinal, _
                        StringComparison.OrdinalIgnoreCase }
        Dim sc As StringComparison
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        Console.WriteLine(intro)
        
        ' Display the current culture because culture affects the result. For example, 
        ' try this code example with the "sv-SE" (Swedish-Sweden) culture.
        Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
        Console.WriteLine("The current culture is ""{0}"" - {1}.", _
                           Thread.CurrentThread.CurrentCulture.Name, _ 
                           Thread.CurrentThread.CurrentCulture.DisplayName)
        
        ' Display the string to search for and the string to search.
        Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
                           CapitalAWithRing, cat)
        Console.WriteLine()
        
        ' Note that in each of the following searches, we look for 
        ' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
        ' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
        ' the string was not found.
        ' Search using different values of StringComparison. Specify the start 
        ' index and count.

        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparison. Specify the 
        ' start index. 

        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, 0, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparison. 

        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub 'Main
End Class 'Sample

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the first occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'

Commenti

Numerazione dell'indice inizia da 0.Index numbering starts from 0. Il parametro startIndex può avere un valore compreso tra 0 e la lunghezza dell'istanza della stringa.The startIndex parameter can range from 0 to the length of the string instance. Se startIndex è uguale alla lunghezza dell'istanza di stringa, il metodo restituisce -1.If startIndex equals the length of the string instance, the method returns -1.

Il comparisonType parametro specifica per cercare il value parametro usando le impostazioni cultura correnti o invariante, tramite una ricerca tra maiuscole e minuscole o maiuscole e minuscole e usando le regole di confronto ordinale o word.The comparisonType parameter specifies to search for the value parameter using the current or invariant culture, using a case-sensitive or case-insensitive search, and using word or ordinal comparison rules.

Note per i chiamanti

I set di caratteri includono caratteri ignorabili, ovvero caratteri che non sono considerati durante l'esecuzione di un confronto linguistico o dipendente dalle impostazioni cultura.Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In una ricerca dipendente dalle impostazioni cultura (ovvero se comparisonType non è Ordinal o OrdinalIgnoreCase), se value contiene un carattere ignorable, il risultato è equivalente alla ricerca con il carattere rimosso.In a culture-sensitive search (that is, if comparisonType is not Ordinal or OrdinalIgnoreCase), if value contains an ignorable character, the result is equivalent to searching with that character removed. Se value costituito solo da uno o più caratteri ignorabili, il IndexOf(String, Int32, StringComparison) metodo restituisce sempre startIndex, ovvero la posizione del carattere in corrispondenza del quale inizia la ricerca.If value consists only of one or more ignorable characters, the IndexOf(String, Int32, StringComparison) method always returns startIndex, which is the character position at which the search begins.

Nell'esempio seguente, il IndexOf(String, Int32, StringComparison) metodo viene usato per trovare la posizione di un segno meno facoltativo (U + 00AD) seguita da una "m" inizia con la terza posizione del carattere in due stringhe.In the following example, the IndexOf(String, Int32, StringComparison) method is used to find the position of a soft hyphen (U+00AD) followed by an "m" starting with the third character position in two strings. Solo una delle stringhe contiene la sottostringa richiesta. Se nell'esempio viene eseguito nel .NET Framework 4.NET Framework 4 o versioni successive, in entrambi i casi, poiché il segno meno facoltativo è un carattere ignorabile, il metodo restituisce l'indice di "m" nella stringa quando esegue un confronto con distinzione delle impostazioni cultura.Only one of the strings contains the required substring.If the example is run on the .NET Framework 4.NET Framework 4 or later, in both cases, because the soft hyphen is an ignorable character, the method returns the index of "m" in the string when it performs a culture-sensitive comparison. Si noti che nel caso della prima stringa, che include il segno meno facoltativo seguito da una "m", il metodo non restituisce l'indice del segno meno facoltativo, ma l'indice di "m".Note that in the case of the first string, which includes the soft hyphen followed by an "m", the method fails to return the index of the soft hyphen but instead returns the index of the "m". Il metodo restituisce l'indice del segno meno facoltativo nella prima stringa solo quando esegue un confronto ordinale.The method returns the index of the soft hyphen in the first string only when it performs an ordinal comparison.

[!code-csharpSystem.String.IndexOf#25] [!code-vbSystem.String.IndexOf#25][!code-csharpSystem.String.IndexOf#25] [!code-vbSystem.String.IndexOf#25]

IndexOf(String, Int32, Int32) IndexOf(String, Int32, Int32) IndexOf(String, Int32, Int32) IndexOf(String, Int32, Int32)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata in questa istanza.Reports the zero-based index of the first occurrence of the specified string in this instance. La ricerca viene eseguita iniziando dalla posizione specificata dei caratteri ed esamina un determinato numero di posizioni.The search starts at a specified character position and examines a specified number of character positions.

public:
 int IndexOf(System::String ^ value, int startIndex, int count);
public int IndexOf (string value, int startIndex, int count);
member this.IndexOf : string * int * int -> int
Public Function IndexOf (value As String, startIndex As Integer, count As Integer) As Integer

Parametri

value
String String String String

Stringa da cercare.The string to seek.

startIndex
Int32 Int32 Int32 Int32

Posizione iniziale della ricerca.The search starting position.

count
Int32 Int32 Int32 Int32

Numero di posizioni dei caratteri da esaminare.The number of character positions to examine.

Restituisce

Posizione dell'indice in base zero di value dall'inizio dell'istanza corrente se la stringa viene trovata oppure -1 in caso contrario.The zero-based index position of value from the start of the current instance if that string is found, or -1 if it is not. Se value è Empty, il valore restituito è startIndex.If value is Empty, the return value is startIndex.

Eccezioni

count o startIndex è negativo.or startIndex is negative.

In alternativa-or- startIndex è maggiore della lunghezza di questa stringa.is greater than the length of this string.

In alternativa-or- count è maggiore della lunghezza di questa stringa meno startIndex.is greater than the length of this string minus startIndex.

Esempi

Nell'esempio seguente trova l'indice di tutte le occorrenze della stringa "he" all'interno di una sottostringa della stringa di un altro.The following example finds the index of all occurrences of the string "he" within a substring of another string. Si noti che il numero di caratteri da cercare deve essere ricalcolato per ogni iterazione di ricerca.Note that the number of characters to be searched must be recalculated for each search iteration.

// Sample for String::IndexOf(String, Int32, Int32)
using namespace System;
int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
   String^ br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
   String^ str = "Now is the time for all good men to come to the aid of their party.";
   int start;
   int at;
   int end;
   int count;
   end = str->Length;
   start = end / 2;
   Console::WriteLine();
   Console::WriteLine( "All occurrences of 'he' from position {0} to {1}.", start, end - 1 );
   Console::WriteLine( "{1}{0}{2}{0}{3}{0}", Environment::NewLine, br1, br2, str );
   Console::Write( "The string 'he' occurs at position(s): " );
   count = 0;
   at = 0;
   while ( (start <= end) && (at > -1) )
   {
      
      // start+count must be a position within -str-.
      count = end - start;
      at = str->IndexOf( "he", start, count );
      if ( at == -1 )
            break;

      Console::Write( "{0} ", at );
      start = at + 1;
   }

   Console::WriteLine();
}

/*
This example produces the following results:

All occurrences of 'he' from position 33 to 66.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 45 56

*/
// Sample for String.IndexOf(String, Int32, Int32)
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;
    int end;
    int count;

    end = str.Length;
    start = end/2;
    Console.WriteLine();
    Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, end-1);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The string 'he' occurs at position(s): ");

    count = 0;
    at = 0;
    while((start <= end) && (at > -1))
        {
// start+count must be a position within -str-.
        count = end - start;
        at = str.IndexOf("he", start, count);
        if (at == -1) break;
        Console.Write("{0} ", at);
        start = at+1;
        }
    Console.WriteLine();
    }
}
/*
This example produces the following results:

All occurrences of 'he' from position 33 to 66.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The string 'he' occurs at position(s): 45 56

*/
' Sample for String.IndexOf(String, Int32, Int32)
Imports System

Class Sample
   
   Public Shared Sub Main()
      
      Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
      Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
      Dim str As String = "Now is the time for all good men to come to the aid of their party."
      Dim start As Integer
      Dim at As Integer
      Dim [end] As Integer
      Dim count As Integer
      
      [end] = str.Length
      start = [end] / 2
      Console.WriteLine()
      Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, [end] - 1)
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The string 'he' occurs at position(s): ")
      
      count = 0
      at = 0
      While start <= [end] AndAlso at > - 1
         ' start+count must be a position within -str-.
         count = [end] - start
         at = str.IndexOf("he", start, count)
         If at = - 1 Then
            Exit While
         End If
         Console.Write("{0} ", at)
         start = at + 1
      End While
      Console.WriteLine()
   End Sub 'Main
End Class 'Sample
'
'This example produces the following results:
'
'All occurrences of 'he' from position 33 to 66.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The string 'he' occurs at position(s): 45 56
'
'

Commenti

Numerazione dell'indice inizia da 0 (zero).Index numbering starts from 0 (zero). Il parametro startIndex può avere un valore compreso tra 0 e la lunghezza dell'istanza della stringa.The startIndex parameter can range from 0 to the length of the string instance.

Questo metodo esegue una ricerca di word (maiuscole/minuscole e distinzione delle impostazioni cultura) usando le impostazioni cultura correnti.This method performs a word (case-sensitive and culture-sensitive) search using the current culture. La ricerca inizia dalla startIndex e continua startIndex + count -1.The search begins at startIndex and continues to startIndex + count -1. Il carattere startIndex + count non è incluso nella ricerca.The character at startIndex + count is not included in the search.

I set di caratteri includono caratteri ignorabili, ovvero caratteri che non sono considerati durante l'esecuzione di un confronto linguistico o dipendente dalle impostazioni cultura.Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In una ricerca dipendente dalle impostazioni cultura, se value contiene un carattere ignorabile, il risultato è equivalente alla ricerca con il carattere rimosso.In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. Se value costituito solo da uno o più caratteri ignorabili, il IndexOf(String, Int32, Int32) metodo restituisce sempre startIndex, ovvero la posizione del carattere in corrispondenza del quale inizia la ricerca.If value consists only of one or more ignorable characters, the IndexOf(String, Int32, Int32) method always returns startIndex, which is the character position at which the search begins. Nell'esempio seguente, il IndexOf(String, Int32, Int32) metodo viene usato per trovare la posizione di un segno meno facoltativo (U + 00AD) seguita da una "m" a partire dal terzo sesto posizioni dei caratteri in due stringhe.In the following example, the IndexOf(String, Int32, Int32) method is used to find the position of a soft hyphen (U+00AD) followed by an "m" starting in the third through sixth character positions in two strings. Solo una delle stringhe contiene la sottostringa richiesta.Only one of the strings contains the required substring. Se nell'esempio viene eseguito nel .NET Framework 4.NET Framework 4 o versioni successive, in entrambi i casi, poiché il segno meno facoltativo è un carattere ignorabile, il metodo restituisce l'indice di "m" nella stringa quando esegue un confronto con distinzione delle impostazioni cultura.If the example is run on the .NET Framework 4.NET Framework 4 or later, in both cases, because the soft hyphen is an ignorable character, the method returns the index of "m" in the string when it performs a culture-sensitive comparison. Si noti che nel caso della prima stringa, che include il segno meno facoltativo seguito da una "m", il metodo non restituisce l'indice del segno meno facoltativo, ma l'indice di "m".Note that in the case of the first string, which includes the soft hyphen followed by an "m", the method fails to return the index of the soft hyphen but instead returns the index of the "m".

using System;

public class Example
{
   public static void Main()
   {
      string searchString = "\u00ADm";
      string s1 = "ani\u00ADmal" ;
      string s2 = "animal";

      Console.WriteLine(s1.IndexOf(searchString, 2, 4));
      Console.WriteLine(s2.IndexOf(searchString, 2, 4));
   }
}
// The example displays the following output:
//       4
//       3
Module Example
   Public Sub Main()
      Dim searchString As String = Chrw(&h00AD) + "m"
      Dim s1 As String = "ani" + ChrW(&h00AD) + "mal"
      Dim s2 As String = "animal"

      Console.WriteLine(s1.IndexOf(searchString, 2, 4))
      Console.WriteLine(s2.IndexOf(searchString, 2, 4))
   End Sub
End Module
' The example displays the following output:
'       4
'       3

Note per i chiamanti

Come illustrato in Best Practices for Using Strings, è consigliabile evitare di chiamare i metodi di confronto tra stringhe che sostituiscono i valori predefiniti e invece chiamano metodi che richiedono parametri per specificare in modo esplicito.As explained in Best Practices for Using Strings, we recommend that you avoid calling string comparison methods that substitute default values and instead call methods that require parameters to be explicitly specified. Per usare le regole di confronto della lingua corrente per eseguire questa operazione, chiamare il IndexOf(String, Int32, Int32, StringComparison) overload del metodo con un valore di CurrentCulture per la relativa comparisonType parametro.To use the comparison rules of the current culture to perform this operation, call the IndexOf(String, Int32, Int32, StringComparison) method overload with a value of CurrentCulture for its comparisonType parameter.

Vedi anche

IndexOf(Char, Int32, Int32) IndexOf(Char, Int32, Int32) IndexOf(Char, Int32, Int32) IndexOf(Char, Int32, Int32)

Restituisce l'indice in base zero della prima occorrenza del carattere specificato in questa istanza.Reports the zero-based index of the first occurrence of the specified character in this instance. La ricerca viene eseguita iniziando dalla posizione specificata dei caratteri ed esamina un determinato numero di posizioni.The search starts at a specified character position and examines a specified number of character positions.

public:
 int IndexOf(char value, int startIndex, int count);
public int IndexOf (char value, int startIndex, int count);
member this.IndexOf : char * int * int -> int
Public Function IndexOf (value As Char, startIndex As Integer, count As Integer) As Integer

Parametri

value
Char Char Char Char

Carattere Unicode da cercare.A Unicode character to seek.

startIndex
Int32 Int32 Int32 Int32

Posizione iniziale della ricerca.The search starting position.

count
Int32 Int32 Int32 Int32

Numero di posizioni dei caratteri da esaminare.The number of character positions to examine.

Restituisce

Posizione dell'indice in base zero di value dall'inizio della stringa se viene trovato il carattere oppure -1 in caso contrario.The zero-based index position of value from the start of the string if that character is found, or -1 if it is not.

Eccezioni

count o startIndex è negativo.or startIndex is negative.

In alternativa-or- startIndex è maggiore della lunghezza di questa stringa.is greater than the length of this string.

In alternativa-or- count è maggiore della lunghezza di questa stringa meno startIndex.is greater than the length of this string minus startIndex.

Esempi

Nell'esempio seguente viene illustrato il IndexOf (metodo).The following example demonstrates the IndexOf method.

// Example for the String::IndexOf( Char, int, int ) method.
using namespace System;
void FindAllChar( Char target, String^ searched )
{
   Console::Write( "The character '{0}' occurs at position(s): ", target );
   int startIndex = -1;
   int hitCount = 0;
   
   // Search for all occurrences of the target.
   while ( true )
   {
      startIndex = searched->IndexOf( target, startIndex + 1, searched->Length - startIndex - 1 );
      
      // Exit the loop if the target is not found.
      if ( startIndex < 0 )
            break;

      Console::Write( "{0}, ", startIndex );
      hitCount++;
   }

   Console::WriteLine( "occurrences: {0}", hitCount );
}

int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----"
   "4----+----5----+----6----+----7";
   String^ br2 = "0123456789012345678901234567890123456789"
   "0123456789012345678901234567890";
   String^ str = "ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi "
   "ABCDEFGHI abcdefghi ABCDEFGHI";
   Console::WriteLine( "This example of String::IndexOf( Char, int, int )\n"
   "generates the following output." );
   Console::WriteLine( "{0}{1}{0}{2}{0}{3}{0}", Environment::NewLine, br1, br2, str );
   FindAllChar( 'A', str );
   FindAllChar( 'a', str );
   FindAllChar( 'I', str );
   FindAllChar( 'i', str );
   FindAllChar( '@', str );
   FindAllChar( ' ', str );
}

/*
This example of String::IndexOf( Char, int, int )
generates the following output.

0----+----1----+----2----+----3----+----4----+----5----+----6----+----7
01234567890123456789012345678901234567890123456789012345678901234567890
ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI

The character 'A' occurs at position(s): 0, 20, 40, 60, occurrences: 4
The character 'a' occurs at position(s): 10, 30, 50, occurrences: 3
The character 'I' occurs at position(s): 8, 28, 48, 68, occurrences: 4
The character 'i' occurs at position(s): 18, 38, 58, occurrences: 3
The character '@' occurs at position(s): occurrences: 0
The character ' ' occurs at position(s): 9, 19, 29, 39, 49, 59, occurrences: 6
*/
// Example for the String.IndexOf( char, int, int ) method.
using System;

class IndexOfCII 
{
    public static void Main() 
    {
        string br1 = 
            "0----+----1----+----2----+----3----+----" +
            "4----+----5----+----6----+----7";
        string br2 = 
            "0123456789012345678901234567890123456789" +
            "0123456789012345678901234567890";
        string str = 
            "ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi " +
            "ABCDEFGHI abcdefghi ABCDEFGHI";

        Console.WriteLine( 
            "This example of String.IndexOf( char, int, int )\n" +
            "generates the following output." );
        Console.WriteLine( 
            "{0}{1}{0}{2}{0}{3}{0}", 
            Environment.NewLine, br1, br2, str );

        FindAllChar( 'A', str );
        FindAllChar( 'a', str );
        FindAllChar( 'I', str );
        FindAllChar( 'i', str );
        FindAllChar( '@', str );
        FindAllChar( ' ', str );
    }

    static void FindAllChar( Char target, String searched )
    {
        Console.Write( 
            "The character '{0}' occurs at position(s): ", 
            target );

        int     startIndex = -1;
        int     hitCount = 0;

        // Search for all occurrences of the target.
        while( true )
        {
            startIndex = searched.IndexOf( 
                target, startIndex + 1, 
                searched.Length - startIndex - 1 );

            // Exit the loop if the target is not found.
            if( startIndex < 0 )
                break;

            Console.Write( "{0}, ", startIndex );
            hitCount++;
        }

        Console.WriteLine( "occurrences: {0}", hitCount );
    }
}

/*
This example of String.IndexOf( char, int, int )
generates the following output.

0----+----1----+----2----+----3----+----4----+----5----+----6----+----7
01234567890123456789012345678901234567890123456789012345678901234567890
ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI

The character 'A' occurs at position(s): 0, 20, 40, 60, occurrences: 4
The character 'a' occurs at position(s): 10, 30, 50, occurrences: 3
The character 'I' occurs at position(s): 8, 28, 48, 68, occurrences: 4
The character 'i' occurs at position(s): 18, 38, 58, occurrences: 3
The character '@' occurs at position(s): occurrences: 0
The character ' ' occurs at position(s): 9, 19, 29, 39, 49, 59, occurrences: 6
*/
' Example for the String.IndexOf( Char, Integer, Integer ) method.
Imports System
Imports Microsoft.VisualBasic

Module IndexOfCII
   
    Sub Main()
        Dim br1 As String = _
            "0----+----1----+----2----+----3----+----" & _
            "4----+----5----+----6----+----7"
        Dim br2 As String = _
            "0123456789012345678901234567890123456789" & _
            "0123456789012345678901234567890"
        Dim str As String = _
            "ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi " & _
            "ABCDEFGHI abcdefghi ABCDEFGHI"
          
        Console.WriteLine( _
            "This example of String.IndexOf( Char, Integer, Integer )" & _
            vbCrLf & "generates the following output." )
        Console.WriteLine( _
            "{0}{1}{0}{2}{0}{3}{0}", _
            Environment.NewLine, br1, br2, str)

        FindAllChar("A"c, str)
        FindAllChar("a"c, str)
        FindAllChar("I"c, str)
        FindAllChar("i"c, str)
        FindAllChar("@"c, str)
        FindAllChar(" "c, str)
    End Sub 'Main
       
    Sub FindAllChar(target As Char, searched As String)

        Console.Write( _
            "The character ""{0}"" occurs at position(s): ", target)
          
        Dim startIndex As Integer = - 1
        Dim hitCount As Integer = 0
          
        ' Search for all occurrences of the target.
        While True
            startIndex = searched.IndexOf( _
                target, startIndex + 1, _
                searched.Length - startIndex - 1)

            ' Exit the loop if the target is not found.
            If startIndex < 0 Then
                Exit While
            End If 

            Console.Write("{0}, ", startIndex)
            hitCount += 1
        End While
          
        Console.WriteLine("occurrences: {0}", hitCount)

    End Sub 'FindAllChar
End Module 'IndexOfCII

' This example of String.IndexOf( Char, Integer, Integer )
' generates the following output.
' 
' 0----+----1----+----2----+----3----+----4----+----5----+----6----+----7
' 01234567890123456789012345678901234567890123456789012345678901234567890
' ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI abcdefghi ABCDEFGHI
' 
' The character "A" occurs at position(s): 0, 20, 40, 60, occurrences: 4
' The character "a" occurs at position(s): 10, 30, 50, occurrences: 3
' The character "I" occurs at position(s): 8, 28, 48, 68, occurrences: 4
' The character "i" occurs at position(s): 18, 38, 58, occurrences: 3
' The character "@" occurs at position(s): occurrences: 0
' The character " " occurs at position(s): 9, 19, 29, 39, 49, 59, occurrences: 6

Commenti

La ricerca inizia dalla startIndex e continua startIndex + count -1.The search begins at startIndex and continues to startIndex + count -1. Il carattere startIndex + count non è incluso nella ricerca.The character at startIndex + count is not included in the search.

Numerazione dell'indice inizia da 0 (zero).Index numbering starts from 0 (zero). Il parametro startIndex può avere un valore compreso tra 0 e la lunghezza dell'istanza della stringa.The startIndex parameter can range from 0 to the length of the string instance.

Questo metodo esegue una ricerca ordinale (cultura), in cui un carattere viene considerato equivalente a un altro solo se i relativi valori scalari Unicode sono uguali.This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. Per eseguire una ricerca dipendente dalle impostazioni cultura, usare il CompareInfo.IndexOf metodo, in cui un valore scalare Unicode che rappresenta un carattere precomposto, ad esempio la legatura "" (U + 00 C 6), potrebbe essere considerato equivalente a tutte le occorrenze di componenti del carattere di correggere sequenza, ad esempio quello "AE" (u+0041, U + 0045), in base alle impostazioni cultura.To perform a culture-sensitive search, use the CompareInfo.IndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature "Æ" (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.

Vedi anche

IndexOf(String, StringComparison) IndexOf(String, StringComparison) IndexOf(String, StringComparison) IndexOf(String, StringComparison)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata nell'oggetto String corrente.Reports the zero-based index of the first occurrence of the specified string in the current String object. Un parametro specifica il tipo di ricerca da usare per la stringa specificata.A parameter specifies the type of search to use for the specified string.

public:
 int IndexOf(System::String ^ value, StringComparison comparisonType);
public int IndexOf (string value, StringComparison comparisonType);
member this.IndexOf : string * StringComparison -> int
Public Function IndexOf (value As String, comparisonType As StringComparison) As Integer

Parametri

value
String String String String

Stringa da cercare.The string to seek.

comparisonType
StringComparison StringComparison StringComparison StringComparison

Uno dei valori di enumerazione che specifica le regole di ricerca.One of the enumeration values that specifies the rules for the search.

Restituisce

Posizione dell'indice del parametro value se tale stringa viene trovata; in caso contrario, -1.The index position of the value parameter if that string is found, or -1 if it is not. Se value è Empty, il valore restituito è 0.If value is Empty, the return value is 0.

Eccezioni

comparisonType non è un valore StringComparison valido.is not a valid StringComparison value.

Esempi

L'esempio seguente illustra tre overload del IndexOf metodo di cui trovare la prima occorrenza di una stringa all'interno di un'altra stringa utilizzando i diversi valori del StringComparison enumerazione.The following example demonstrates three overloads of the IndexOf method that find the first occurrence of a string within another string using different values of the StringComparison enumeration.

// This code example demonstrates the 
// System.String.IndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the first occurrence of a character using different " + 
                   "values of StringComparison.";
    string resultFmt = "Comparison: {0,-28} Location: {1,3}";

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string CapitalAWithRing = "\u00c5"; 

// Define a string to search. 
// The result of combining the characters LATIN SMALL LETTER A and COMBINING 
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
    string cat = "A Cheshire c" + "\u0061\u030a" + "t";

    int loc = 0;
    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

// Clear the screen and display an introduction.
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because culture affects the result. For example, 
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Console.WriteLine("The current culture is \"{0}\" - {1}.", 
                       Thread.CurrentThread.CurrentCulture.Name,
                       Thread.CurrentThread.CurrentCulture.DisplayName);

// Display the string to search for and the string to search.
    Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"", 
                       CapitalAWithRing, cat);
    Console.WriteLine();

// Note that in each of the following searches, we look for 
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
// the string was not found.
// Search using different values of StringComparison. Specify the start 
// index and count. 

    Console.WriteLine("Part 1: Start index and count are specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparison. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, 0, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparison. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }
    }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the first occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/
' This code example demonstrates the 
' System.String.IndexOf(String, ..., StringComparison) methods.

Imports System
Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the first occurrence of a character using different " & _
                              "values of StringComparison."
        Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
        
        ' Define a string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim CapitalAWithRing As String = "Å"
        
        ' Define a string to search. 
        ' The result of combining the characters LATIN SMALL LETTER A and COMBINING 
        ' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
        ' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
        Dim cat As String = "A Cheshire c" & "å" & "t"
        
        Dim loc As Integer = 0
        Dim scValues As StringComparison() =  { _
                        StringComparison.CurrentCulture, _
                        StringComparison.CurrentCultureIgnoreCase, _
                        StringComparison.InvariantCulture, _
                        StringComparison.InvariantCultureIgnoreCase, _
                        StringComparison.Ordinal, _
                        StringComparison.OrdinalIgnoreCase }
        Dim sc As StringComparison
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        Console.WriteLine(intro)
        
        ' Display the current culture because culture affects the result. For example, 
        ' try this code example with the "sv-SE" (Swedish-Sweden) culture.
        Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
        Console.WriteLine("The current culture is ""{0}"" - {1}.", _
                           Thread.CurrentThread.CurrentCulture.Name, _ 
                           Thread.CurrentThread.CurrentCulture.DisplayName)
        
        ' Display the string to search for and the string to search.
        Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
                           CapitalAWithRing, cat)
        Console.WriteLine()
        
        ' Note that in each of the following searches, we look for 
        ' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
        ' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
        ' the string was not found.
        ' Search using different values of StringComparison. Specify the start 
        ' index and count.

        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparison. Specify the 
        ' start index. 

        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, 0, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparison. 

        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub 'Main
End Class 'Sample

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the first occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'

Commenti

Numerazione dell'indice inizia da zero.Index numbering starts from zero.

Il comparisonType parametro specifica per cercare il value parametro usando le impostazioni cultura correnti o invariante, tramite una ricerca tra maiuscole e minuscole o maiuscole e minuscole e usando le regole di confronto ordinale o word.The comparisonType parameter specifies to search for the value parameter using the current or invariant culture, using a case-sensitive or case-insensitive search, and using word or ordinal comparison rules.

Note per i chiamanti

I set di caratteri includono caratteri ignorabili, ovvero caratteri che non sono considerati durante l'esecuzione di un confronto linguistico o dipendente dalle impostazioni cultura.Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In una ricerca dipendente dalle impostazioni cultura (ovvero se comparisonType non è Ordinal o OrdinalIgnoreCase), se value contiene un carattere ignorable, il risultato è equivalente alla ricerca con il carattere rimosso.In a culture-sensitive search (that is, if comparisonType is not Ordinal or OrdinalIgnoreCase), if value contains an ignorable character, the result is equivalent to searching with that character removed. Se value costituito solo da uno o più caratteri ignorabili, il IndexOf(String, StringComparison) metodo restituisce sempre 0 (zero) per indicare che non viene trovata la corrispondenza all'inizio dell'istanza corrente.If value consists only of one or more ignorable characters, the IndexOf(String, StringComparison) method always returns 0 (zero) to indicate that the match is found at the beginning of the current instance.

Nell'esempio seguente, il IndexOf(String, StringComparison) metodo viene usato per trovare tre sottostringhe (un segno meno facoltativo (U + 00AD), un segno meno facoltativo seguito da "n" e un segno meno facoltativo seguito da "m") in due stringhe.In the following example, the IndexOf(String, StringComparison) method is used to find three substrings (a soft hyphen (U+00AD), a soft hyphen followed by "n", and a soft hyphen followed by "m") in two strings. Solo una delle stringhe contiene un segno meno facoltativo.Only one of the strings contains a soft hyphen. Se nell'esempio viene eseguito nel .NET Framework 4.NET Framework 4 o versioni successive, poiché il segno meno facoltativo è un carattere ignorabile, una ricerca dipendente dalle impostazioni cultura restituisce lo stesso valore che verrebbe restituito se il segno meno facoltativo non incluse nella stringa di ricerca.If the example is run on the .NET Framework 4.NET Framework 4 or later, because the soft hyphen is an ignorable character, a culture-sensitive search returns the same value that it would return if the soft hyphen were not included in the search string. Una ricerca ordinale, tuttavia, correttamente consente di trovare il segno meno facoltativo in una stringa e segnala che è assente dalla seconda stringa.An ordinal search, however, successfully finds the soft hyphen in one string and reports that it is absent from the second string.

[!code-csharpSystem.String.IndexOf#26] [!code-vbSystem.String.IndexOf#26][!code-csharpSystem.String.IndexOf#26] [!code-vbSystem.String.IndexOf#26]

IndexOf(String, Int32, Int32, StringComparison) IndexOf(String, Int32, Int32, StringComparison) IndexOf(String, Int32, Int32, StringComparison) IndexOf(String, Int32, Int32, StringComparison)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata nell'oggetto String corrente.Reports the zero-based index of the first occurrence of the specified string in the current String object. I parametri specificano la posizione di ricerca iniziale nella stringa corrente, il numero di caratteri nella stringa corrente in cui eseguire la ricerca e il tipo di ricerca da usare per la stringa specificata.Parameters specify the starting search position in the current string, the number of characters in the current string to search, and the type of search to use for the specified string.

public:
 int IndexOf(System::String ^ value, int startIndex, int count, StringComparison comparisonType);
public int IndexOf (string value, int startIndex, int count, StringComparison comparisonType);
member this.IndexOf : string * int * int * StringComparison -> int
Public Function IndexOf (value As String, startIndex As Integer, count As Integer, comparisonType As StringComparison) As Integer

Parametri

value
String String String String

Stringa da cercare.The string to seek.

startIndex
Int32 Int32 Int32 Int32

Posizione iniziale della ricerca.The search starting position.

count
Int32 Int32 Int32 Int32

Numero di posizioni dei caratteri da esaminare.The number of character positions to examine.

comparisonType
StringComparison StringComparison StringComparison StringComparison

Uno dei valori di enumerazione che specifica le regole di ricerca.One of the enumeration values that specifies the rules for the search.

Restituisce

Posizione dell'indice in base zero del parametro value dall'inizio dell'istanza corrente se la stringa viene trovata oppure -1 in caso contrario.The zero-based index position of the value parameter from the start of the current instance if that string is found, or -1 if it is not. Se value è Empty, il valore restituito è startIndex.If value is Empty, the return value is startIndex.

Eccezioni

count o startIndex è negativo.or startIndex is negative.

In alternativa-or- startIndex è maggiore della lunghezza di questa istanza.is greater than the length of this instance.

In alternativa-or- count è maggiore della lunghezza di questa stringa meno startIndex.is greater than the length of this string minus startIndex.

comparisonType non è un valore StringComparison valido.is not a valid StringComparison value.

Esempi

L'esempio seguente illustra tre overload del IndexOf metodo di cui trovare la prima occorrenza di una stringa all'interno di un'altra stringa utilizzando i diversi valori del StringComparison enumerazione.The following example demonstrates three overloads of the IndexOf method that find the first occurrence of a string within another string using different values of the StringComparison enumeration.

// This code example demonstrates the 
// System.String.IndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the first occurrence of a character using different " + 
                   "values of StringComparison.";
    string resultFmt = "Comparison: {0,-28} Location: {1,3}";

// Define a string to search for.
// U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
    string CapitalAWithRing = "\u00c5"; 

// Define a string to search. 
// The result of combining the characters LATIN SMALL LETTER A and COMBINING 
// RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
// LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
    string cat = "A Cheshire c" + "\u0061\u030a" + "t";

    int loc = 0;
    StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

// Clear the screen and display an introduction.
    Console.Clear();
    Console.WriteLine(intro);

// Display the current culture because culture affects the result. For example, 
// try this code example with the "sv-SE" (Swedish-Sweden) culture.

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Console.WriteLine("The current culture is \"{0}\" - {1}.", 
                       Thread.CurrentThread.CurrentCulture.Name,
                       Thread.CurrentThread.CurrentCulture.DisplayName);

// Display the string to search for and the string to search.
    Console.WriteLine("Search for the string \"{0}\" in the string \"{1}\"", 
                       CapitalAWithRing, cat);
    Console.WriteLine();

// Note that in each of the following searches, we look for 
// LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
// LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
// the string was not found.
// Search using different values of StringComparison. Specify the start 
// index and count. 

    Console.WriteLine("Part 1: Start index and count are specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparison. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, 0, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparison. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.IndexOf(CapitalAWithRing, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }
    }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the first occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/
' This code example demonstrates the 
' System.String.IndexOf(String, ..., StringComparison) methods.

Imports System
Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the first occurrence of a character using different " & _
                              "values of StringComparison."
        Dim resultFmt As String = "Comparison: {0,-28} Location: {1,3}"
        
        ' Define a string to search for.
        ' U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
        Dim CapitalAWithRing As String = "Å"
        
        ' Define a string to search. 
        ' The result of combining the characters LATIN SMALL LETTER A and COMBINING 
        ' RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
        ' LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
        Dim cat As String = "A Cheshire c" & "å" & "t"
        
        Dim loc As Integer = 0
        Dim scValues As StringComparison() =  { _
                        StringComparison.CurrentCulture, _
                        StringComparison.CurrentCultureIgnoreCase, _
                        StringComparison.InvariantCulture, _
                        StringComparison.InvariantCultureIgnoreCase, _
                        StringComparison.Ordinal, _
                        StringComparison.OrdinalIgnoreCase }
        Dim sc As StringComparison
        
        ' Clear the screen and display an introduction.
        Console.Clear()
        Console.WriteLine(intro)
        
        ' Display the current culture because culture affects the result. For example, 
        ' try this code example with the "sv-SE" (Swedish-Sweden) culture.
        Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
        Console.WriteLine("The current culture is ""{0}"" - {1}.", _
                           Thread.CurrentThread.CurrentCulture.Name, _ 
                           Thread.CurrentThread.CurrentCulture.DisplayName)
        
        ' Display the string to search for and the string to search.
        Console.WriteLine("Search for the string ""{0}"" in the string ""{1}""", _
                           CapitalAWithRing, cat)
        Console.WriteLine()
        
        ' Note that in each of the following searches, we look for 
        ' LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
        ' LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
        ' the string was not found.
        ' Search using different values of StringComparison. Specify the start 
        ' index and count.

        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparison. Specify the 
        ' start index. 

        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, 0, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparison. 

        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.IndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub 'Main
End Class 'Sample

'
'Note: This code example was executed on a console whose user interface 
'culture is "en-US" (English-United States).
'
'This code example produces the following results:
'
'Find the first occurrence of a character using different values of StringComparison.
'The current culture is "en-US" - English (United States).
'Search for the string "Å" in the string "A Cheshire ca°t"
'
'Part 1: Start index and count are specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 2: Start index is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'
'Part 3: Neither start index nor count is specified.
'Comparison: CurrentCulture               Location:  -1
'Comparison: CurrentCultureIgnoreCase     Location:  12
'Comparison: InvariantCulture             Location:  -1
'Comparison: InvariantCultureIgnoreCase   Location:  12
'Comparison: Ordinal                      Location:  -1
'Comparison: OrdinalIgnoreCase            Location:  -1
'

Commenti

Numerazione dell'indice inizia da 0 (zero).Index numbering starts from 0 (zero). Il parametro startIndex può avere un valore compreso tra 0 e la lunghezza dell'istanza della stringa.The startIndex parameter can range from 0 to the length of the string instance.

La ricerca inizia dalla startIndex e continua startIndex + count -1.The search begins at startIndex and continues to startIndex + count -1. Il carattere startIndex + count non è incluso nella ricerca.The character at startIndex + count is not included in the search.

Il comparisonType parametro specifica per cercare il value parametro usando le impostazioni cultura correnti o invariante, tramite una ricerca tra maiuscole e minuscole o maiuscole e minuscole e usando le regole di confronto ordinale o word.The comparisonType parameter specifies to search for the value parameter using the current or invariant culture, using a case-sensitive or case-insensitive search, and using word or ordinal comparison rules.

Note per i chiamanti

I set di caratteri includono caratteri ignorabili, ovvero caratteri che non sono considerati durante l'esecuzione di un confronto linguistico o dipendente dalle impostazioni cultura.Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In una ricerca dipendente dalle impostazioni cultura (ovvero se comparisonType non è Ordinal o OrdinalIgnoreCase), se value contiene un carattere ignorable, il risultato è equivalente alla ricerca con il carattere rimosso.In a culture-sensitive search (that is, if comparisonType is not Ordinal or OrdinalIgnoreCase), if value contains an ignorable character, the result is equivalent to searching with that character removed. Se value costituito solo da uno o più caratteri ignorabili, il IndexOf(String, Int32, Int32, StringComparison) metodo restituisce sempre startIndex, ovvero la posizione del carattere in corrispondenza del quale inizia la ricerca.If value consists only of one or more ignorable characters, the IndexOf(String, Int32, Int32, StringComparison) method always returns startIndex, which is the character position at which the search begins.

Nell'esempio seguente, il IndexOf(String, Int32, Int32, StringComparison) metodo viene usato per trovare la posizione di un segno meno facoltativo (U + 00AD) seguita da una "m" a partire dal terzo sesto posizioni dei caratteri in due stringhe.In the following example, the IndexOf(String, Int32, Int32, StringComparison) method is used to find the position of a soft hyphen (U+00AD) followed by an "m" starting in the third through sixth character positions in two strings. Solo una delle stringhe contiene la sottostringa richiesta.Only one of the strings contains the required substring. Se nell'esempio viene eseguito nel .NET Framework 4.NET Framework 4 o versioni successive, in entrambi i casi, poiché il segno meno facoltativo è un carattere ignorabile, il metodo restituisce l'indice di "m" nella stringa quando esegue un confronto con distinzione delle impostazioni cultura.If the example is run on the .NET Framework 4.NET Framework 4 or later, in both cases, because the soft hyphen is an ignorable character, the method returns the index of "m" in the string when it performs a culture-sensitive comparison. Quando esegue un confronto ordinale, tuttavia, trova la sottostringa solo nella prima stringa.When it performs an ordinal comparison, however, it finds the substring only in the first string. Si noti che nel caso della prima stringa, che include il segno meno facoltativo seguito da una "m", il metodo non restituisce l'indice del segno ma restituisce l'indice di "m" quando esegue un confronto con distinzione delle impostazioni cultura.Note that in the case of the first string, which includes the soft hyphen followed by an "m", the method fails to return the index of the soft hyphen but instead returns the index of the "m" when it performs a culture-sensitive comparison. Il metodo restituisce l'indice del segno meno facoltativo nella prima stringa solo quando esegue un confronto ordinale.The method returns the index of the soft hyphen in the first string only when it performs an ordinal comparison.

[!code-csharpSystem.String.IndexOf#24] [!code-vbSystem.String.IndexOf#24][!code-csharpSystem.String.IndexOf#24] [!code-vbSystem.String.IndexOf#24]

IndexOf(Char, StringComparison) IndexOf(Char, StringComparison) IndexOf(Char, StringComparison) IndexOf(Char, StringComparison)

Restituisce l'indice in base zero della prima occorrenza del carattere Unicode specificato in questa stringa.Reports the zero-based index of the first occurrence of the specified Unicode character in this string. Un parametro specifica il tipo di ricerca da usare per il carattere specificato.A parameter specifies the type of search to use for the specified character.

public:
 int IndexOf(char value, StringComparison comparisonType);
public int IndexOf (char value, StringComparison comparisonType);
member this.IndexOf : char * StringComparison -> int
Public Function IndexOf (value As Char, comparisonType As StringComparison) As Integer

Parametri

value
Char Char Char Char

Il carattere da cercare.The character to seek.

comparisonType
StringComparison StringComparison StringComparison StringComparison

Un valore di enumerazione che specifica le regole per la ricerca.An enumeration value that specifies the rules for the search.

Restituisce

Posizione dell'indice in base zero di value se viene trovato il carattere, in caso contrario -1.The zero-based index of value if that character is found, or -1 if it is not.

Eccezioni

comparisonType non è un valore StringComparison valido.is not a valid StringComparison value.

Commenti

Numerazione dell'indice inizia da zero.Index numbering starts from zero.

Il comparisonType parametro è un StringComparison membro di enumerazione che specifica se la ricerca per il value argomento utilizza le impostazioni cultura correnti o invariante, è distinzione maiuscole/minuscole o maiuscole e minuscole o utilizza le regole di confronto ordinale o word.The comparisonType parameter is a StringComparison enumeration member that specifies whether the search for the value argument uses the current or invariant culture, is case-sensitive or case-insensitive, or uses word or ordinal comparison rules.

IndexOf(Char, Int32) IndexOf(Char, Int32) IndexOf(Char, Int32) IndexOf(Char, Int32)

Restituisce l'indice in base zero della prima occorrenza del carattere Unicode specificato in questa stringa.Reports the zero-based index of the first occurrence of the specified Unicode character in this string. La ricerca ha inizio alla posizione del carattere specificata.The search starts at a specified character position.

public:
 int IndexOf(char value, int startIndex);
public int IndexOf (char value, int startIndex);
member this.IndexOf : char * int -> int
Public Function IndexOf (value As Char, startIndex As Integer) As Integer

Parametri

value
Char Char Char Char

Carattere Unicode da cercare.A Unicode character to seek.

startIndex
Int32 Int32 Int32 Int32

Posizione iniziale della ricerca.The search starting position.

Restituisce

Posizione dell'indice in base zero di value dall'inizio della stringa se viene trovato il carattere oppure -1 in caso contrario.The zero-based index position of value from the start of the string if that character is found, or -1 if it is not.

Eccezioni

startIndex è minore di 0 (zero) o maggiore della lunghezza della stringa.is less than 0 (zero) or greater than the length of the string.

Esempi

Nell'esempio seguente viene illustrato il IndexOf (metodo).The following example demonstrates the IndexOf method.

// Sample for String::IndexOf(Char, Int32)
using namespace System;
int main()
{
   String^ br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
   String^ br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
   String^ str = "Now is the time for all good men to come to the aid of their party.";
   int start;
   int at;
   Console::WriteLine();
   Console::WriteLine( "All occurrences of 't' from position 0 to {0}.", str->Length - 1 );
   Console::WriteLine( "{1}{0}{2}{0}{3}{0}", Environment::NewLine, br1, br2, str );
   Console::Write( "The letter 't' occurs at position(s): " );
   at = 0;
   start = 0;
   while ( (start < str->Length) && (at > -1) )
   {
      at = str->IndexOf( 't', start );
      if ( at == -1 )
            break;

      Console::Write( "{0} ", at );
      start = at + 1;
   }

   Console::WriteLine();
}

/*
This example produces the following results:

All occurrences of 't' from position 0 to 66.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 7 11 33 41 44 55 64

*/
// Sample for String.IndexOf(Char, Int32)
using System;

class Sample {
    public static void Main() {

    string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
    string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
    string str = "Now is the time for all good men to come to the aid of their party.";
    int start;
    int at;

    Console.WriteLine();
    Console.WriteLine("All occurrences of 't' from position 0 to {0}.", str.Length-1);
    Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str);
    Console.Write("The letter 't' occurs at position(s): ");

    at = 0;
    start = 0; 
    while((start < str.Length) && (at > -1))
        {
        at = str.IndexOf('t', start);
        if (at == -1) break;
        Console.Write("{0} ", at);
        start = at+1;
        }
    Console.WriteLine();
    }
}
/*
This example produces the following results:

All occurrences of 't' from position 0 to 66.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.

The letter 't' occurs at position(s): 7 11 33 41 44 55 64

*/
' Sample for String.IndexOf(Char, Int32)

Module Sample
    Sub Main()

        Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
        Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
        Dim str As String = "Now is the time for all good men to come to the aid of their party."
        Dim start As Integer
        Dim at As Integer

        Console.WriteLine()
        Console.WriteLine("All occurrences of 't' from position 0 to {0}.", str.Length - 1)
        Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
        Console.Write("The letter 't' occurs at position(s): ")

        at = 0
        start = 0
        While start < str.Length AndAlso at > -1
            at = str.IndexOf("t"c, start)
            If at = -1 Then
                Exit While
            End If
            Console.Write("{0} ", at)
            start = at + 1
        End While
        Console.WriteLine()
    End Sub
End Module
'
'This example produces the following results:
'
'All occurrences of 't' from position 0 to 66.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The letter 't' occurs at position(s): 7 11 33 41 44 55 64
'
'

Commenti

Numerazione dell'indice inizia da 0.Index numbering starts from 0. Il parametro startIndex può avere un valore compreso tra 0 e la lunghezza dell'istanza della stringa.The startIndex parameter can range from 0 to the length of the string instance. Se startIndex è uguale alla lunghezza dell'istanza di stringa, il metodo restituisce -1.If startIndex equals the length of the string instance, the method returns -1.

La ricerca sarà compreso startIndex alla fine della stringa.The search ranges from startIndex to the end of the string.

Questo metodo esegue una ricerca ordinale (cultura), in cui un carattere viene considerato equivalente a un altro solo se i relativi valori scalari Unicode sono uguali.This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. Per eseguire una ricerca dipendente dalle impostazioni cultura, usare il CompareInfo.IndexOf metodo, in cui un valore scalare Unicode che rappresenta un carattere precomposto, ad esempio la legatura "" (U + 00 C 6), potrebbe essere considerato equivalente a tutte le occorrenze di componenti del carattere di correggere sequenza, ad esempio quello "AE" (u+0041, U + 0045), in base alle impostazioni cultura.To perform a culture-sensitive search, use the CompareInfo.IndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature "Æ" (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.

Vedi anche

IndexOf(String) IndexOf(String) IndexOf(String) IndexOf(String)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata in questa istanza.Reports the zero-based index of the first occurrence of the specified string in this instance.

public:
 int IndexOf(System::String ^ value);
public int IndexOf (string value);
member this.IndexOf : string -> int
Public Function IndexOf (value As String) As Integer

Parametri

value
String String String String

Stringa da cercare.The string to seek.

Restituisce

Posizione dell'indice in base zero di value se viene trovata la stringa; in caso contrario, -1.The zero-based index position of value if that string is found, or -1 if it is not. Se value è Empty, il valore restituito è 0.If value is Empty, the return value is 0.

Eccezioni

Esempi

Nell'esempio seguente esegue la ricerca per "n" in "animali".The following example searches for the "n" in "animal". Poiché gli indici di stringa iniziano da zero anziché a uno, il IndexOf(String) metodo indica che "n" è nella posizione 1.Because string indexes begin at zero rather than one, the IndexOf(String) method indicates that the "n" is at position 1.

using namespace System;

void main()
{
   String^ str = "animal";
   String^ toFind = "n";
   int index = str->IndexOf("n");
   Console::WriteLine("Found '{0}' in '{1}' at position {2}",
                        toFind, str, index);

}
// The example displays the following output:
//        Found 'n' in 'animal' at position 1
using System;

public class Example
{
   public static void Main()
   {
      String str = "animal";
      String toFind = "n";
      int index = str.IndexOf("n");
      Console.WriteLine("Found '{0}' in '{1}' at position {2}",
                        toFind, str, index);
   }
}
// The example displays the following output:
//        Found 'n' in 'animal' at position 1
Public Module Example
   Public Sub Main()
      Dim str As String = "animal"
      Dim toFind As String = "n"
      Dim index As Integer = str.IndexOf("n")
      Console.WriteLine("Found '{0}' in '{1}' at position {2}",
                        toFind, str, index)
   End Sub
End Module
' The example displays the following output:
'       Found 'n' in 'animal' at position 1

L'esempio seguente usa il IndexOf metodo per determinare la posizione iniziale di un nome di polizia di una frase.The following example uses the IndexOf method to determine the starting position of an animal name in a sentence. Questa posizione viene quindi utilizzata per inserire un aggettivo descritti animale nella frase.It then uses this position to insert an adjective that describes the animal into the sentence.

using namespace System;

int main()
{
   String^ animal1 = "fox";
   String^ animal2 = "dog";
   String^ strTarget = String::Format( "The {0} jumps over the {1}.", animal1, animal2 );
   Console::WriteLine( "The original string is:{0}{1}{0}", Environment::NewLine, strTarget );
   Console::Write( "Enter an adjective (or group of adjectives) to describe the {0}: ==> ", animal1 );
   String^ adj1 = Console::ReadLine();
   Console::Write( "Enter an adjective (or group of adjectives) to describe the {0}: ==> ", animal2 );
   String^ adj2 = Console::ReadLine();
   adj1 = String::Concat( adj1->Trim(), " " );
   adj2 = String::Concat( adj2->Trim(), " " );
   strTarget = strTarget->Insert( strTarget->IndexOf( animal1 ), adj1 );
   strTarget = strTarget->Insert( strTarget->IndexOf( animal2 ), adj2 );
   Console::WriteLine( " {0}The final string is: {0} {1}", Environment::NewLine, strTarget );
}
// Output from the example might appear as follows:
//       The original string is:
//       The fox jumps over the dog.
//       
//       Enter an adjective (or group of adjectives) to describe the fox: ==> bold
//       Enter an adjective (or group of adjectives) to describe the dog: ==> lazy
//       
//       The final string is:
//       The bold fox jumps over the lazy dog.
using System;

public class Example {
    public static void Main() 
    {
        string animal1 = "fox";
        string animal2 = "dog";

        string strTarget = String.Format("The {0} jumps over the {1}.", 
                                         animal1, animal2);

        Console.WriteLine("The original string is:{0}{1}{0}", 
                          Environment.NewLine, strTarget);

        Console.Write("Enter an adjective (or group of adjectives) " +
                      "to describe the {0}: ==> ", animal1);
        string adj1 = Console.ReadLine();

        Console.Write("Enter an adjective (or group of adjectives) " + 
                      "to describe the {0}: ==> ", animal2);    
        string adj2 = Console.ReadLine();

        adj1 = adj1.Trim() + " ";
        adj2 = adj2.Trim() + " ";

        strTarget = strTarget.Insert(strTarget.IndexOf(animal1), adj1);
        strTarget = strTarget.Insert(strTarget.IndexOf(animal2), adj2);

        Console.WriteLine("{0}The final string is:{0}{1}", 
                          Environment.NewLine, strTarget);
    }
}
// Output from the example might appear as follows:
//       The original string is:
//       The fox jumps over the dog.
//       
//       Enter an adjective (or group of adjectives) to describe the fox: ==> bold
//       Enter an adjective (or group of adjectives) to describe the dog: ==> lazy
//       
//       The final string is:
//       The bold fox jumps over the lazy dog.
Public Class Example
    Public Shared Sub Main()
        Dim animal1 As String = "fox"
        Dim animal2 As String = "dog"
        Dim strTarget As String = String.Format("The {0} jumps over the {1}.", 
                                                animal1, animal2)
        
        Console.WriteLine("The original string is: {0}{1}{0}", 
                          Environment.NewLine, strTarget)
        
        Console.Write("Enter an adjective (or group of adjectives) " +
                      "to describe the {0}: ==> ", animal1)
        Dim adj1 As String = Console.ReadLine()
        
        Console.Write("Enter an adjective (or group of adjectives) " + 
                      "to describe the {0}: ==> ", animal2)
        Dim adj2 As String = Console.ReadLine()
        
        adj1 = adj1.Trim() + " "
        adj2 = adj2.Trim() + " "
        
        strTarget = strTarget.Insert(strTarget.IndexOf(animal1), adj1)
        strTarget = strTarget.Insert(strTarget.IndexOf(animal2), adj2)
        
        Console.WriteLine("{0}The final string is:{0}{1}", 
                          Environment.NewLine, strTarget)
    End Sub 
End Class 
' Output from the example might appear as follows:
'       The original string is:
'       The fox jumps over the dog.
'       
'       Enter an adjective (or group of adjectives) to describe the fox: ==> bold
'       Enter an adjective (or group of adjectives) to describe the dog: ==> lazy
'       
'       The final string is:
'       The bold fox jumps over the lazy dog.

Commenti

Numerazione dell'indice inizia da zero.Index numbering starts from zero.

Questo metodo esegue una ricerca di word (maiuscole/minuscole e distinzione delle impostazioni cultura) usando le impostazioni cultura correnti.This method performs a word (case-sensitive and culture-sensitive) search using the current culture. La ricerca inizia nella posizione del primo carattere di questa istanza e continua fino a quando l'ultima posizione di carattere.The search begins at the first character position of this instance and continues until the last character position.

I set di caratteri includono caratteri ignorabili, ovvero caratteri che non sono considerati durante l'esecuzione di un confronto linguistico o dipendente dalle impostazioni cultura.Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In una ricerca dipendente dalle impostazioni cultura, se value contiene un carattere ignorabile, il risultato è equivalente alla ricerca con il carattere rimosso.In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. Se value costituito solo da uno o più caratteri ignorabili, il IndexOf(String) metodo restituisce sempre 0 (zero) per indicare che non viene trovata la corrispondenza all'inizio dell'istanza corrente.If value consists only of one or more ignorable characters, the IndexOf(String) method always returns 0 (zero) to indicate that the match is found at the beginning of the current instance. Nell'esempio seguente, il IndexOf(String) metodo viene usato per trovare tre sottostringhe (un segno meno facoltativo (U + 00AD), un segno meno facoltativo seguito da "n" e un segno meno facoltativo seguito da "m") in due stringhe.In the following example, the IndexOf(String) method is used to find three substrings (a soft hyphen (U+00AD), a soft hyphen followed by "n", and a soft hyphen followed by "m") in two strings. Solo una delle stringhe contiene un segno meno facoltativo.Only one of the strings contains a soft hyphen. Se nell'esempio viene eseguito nel .NET Framework 4.NET Framework 4 o versioni successive, in ogni caso, poiché il segno meno facoltativo è un carattere ignorabile, il risultato è lo stesso come se il segno meno facoltativo non era stato incluso in value.If the example is run on the .NET Framework 4.NET Framework 4 or later, in each case, because the soft hyphen is an ignorable character, the result is the same as if the soft hyphen had not been included in value. Quando si cercano un segno meno facoltativo solo, il metodo restituisce 0 (zero) per indicare che ha trovato una corrispondenza all'inizio della stringa.When searching for a soft hyphen only, the method returns 0 (zero) to indicate that it has found a match at the beginning of the string.

using System;

public class Example
{
   public static void Main()
   {
      string s1 = "ani\u00ADmal";
      string s2 = "animal";
      
      // Find the index of the soft hyphen.
      Console.WriteLine(s1.IndexOf("\u00AD"));
      Console.WriteLine(s2.IndexOf("\u00AD"));
      
      // Find the index of the soft hyphen followed by "n".
      Console.WriteLine(s1.IndexOf("\u00ADn"));
      Console.WriteLine(s2.IndexOf("\u00ADn"));
      
      // Find the index of the soft hyphen followed by "m".
      Console.WriteLine(s1.IndexOf("\u00ADm"));
      Console.WriteLine(s2.IndexOf("\u00ADm"));
   }
}
// The example displays the following output
// if run under the .NET Framework 4 or later:
//       0
//       0
//       1
//       1
//       4
//       3
Module Example
   Public Sub Main()
      Dim softHyphen As String = ChrW(&h00AD)
      Dim s1 As String = "ani" + softHyphen + "mal"
      Dim s2 As String = "animal"
      
      ' Find the index of the soft hyphen.
      Console.WriteLine(s1.IndexOf(softHyphen))
      Console.WriteLine(s2.IndexOf(softHyphen))
      
      ' Find the index of the soft hyphen followed by "n".
      Console.WriteLine(s1.IndexOf(softHyphen + "n"))
      Console.WriteLine(s2.IndexOf(softHyphen + "n"))
      
      ' Find the index of the soft hyphen followed by "m".
      Console.WriteLine(s1.IndexOf(softHyphen + "m"))
      Console.WriteLine(s2.IndexOf(softHyphen + "m"))
   End Sub
End Module
' The example displays the following output 
' if run under the .NET Framework 4 or later:
'       0
'       0
'       1
'       1
'       4
'       3

Note per i chiamanti

Come illustrato in Best Practices for Using Strings, è consigliabile evitare di chiamare i metodi di confronto tra stringhe che sostituiscono i valori predefiniti e invece chiamano metodi che richiedono parametri per specificare in modo esplicito.As explained in Best Practices for Using Strings, we recommend that you avoid calling string comparison methods that substitute default values and instead call methods that require parameters to be explicitly specified. Per trovare il primo indice di una sottostringa all'interno di un'istanza di stringa usando le regole di confronto delle impostazioni cultura correnti, chiamare il IndexOf(String, StringComparison) overload del metodo con un valore di CurrentCulture per la relativa comparisonType parametro.To find the first index of a substring within a string instance by using the comparison rules of the current culture, call the IndexOf(String, StringComparison) method overload with a value of CurrentCulture for its comparisonType parameter.

Vedi anche

IndexOf(Char) IndexOf(Char) IndexOf(Char) IndexOf(Char)

Restituisce l'indice in base zero della prima occorrenza del carattere Unicode specificato in questa stringa.Reports the zero-based index of the first occurrence of the specified Unicode character in this string.

public:
 int IndexOf(char value);
public int IndexOf (char value);
member this.IndexOf : char -> int
Public Function IndexOf (value As Char) As Integer

Parametri

value
Char Char Char Char

Carattere Unicode da cercare.A Unicode character to seek.

Restituisce

Posizione dell'indice in base zero di value se viene trovato il carattere; in caso contrario, -1.The zero-based index position of value if that character is found, or -1 if it is not.

Esempi

Nell'esempio seguente viene illustrato come è possibile cercare un String di un carattere utilizzando il IndexOf (metodo).The following example demonstrates how you can search a String for a character using the IndexOf method.

using namespace System;

void main()
{
   // Create a Unicode String with 5 Greek Alpha characters.
   String^ szGreekAlpha = gcnew String(L'\x0391',5);

   // Create a Unicode String with a 3 Greek Omega characters.
   String^ szGreekOmega = L"\x03A9\x03A9\x03A9";

   String^ szGreekLetters = String::Concat(szGreekOmega, szGreekAlpha, 
                                           szGreekOmega->Clone());

   // Display the entire string.
   Console::WriteLine(szGreekLetters);

   // The first index of Alpha.
   int ialpha = szGreekLetters->IndexOf( L'\x0391');
   // The first index of Omega.
   int iomega = szGreekLetters->IndexOf(L'\x03A9');

   Console::WriteLine("First occurrence of the Greek letter Alpha: Index {0}", 
                      ialpha);
   Console::WriteLine("First occurrence of the Greek letter Omega: Index {0}", 
                      iomega);
}
// The example displays the following output:
//       The string: OOO?????OOO
//       First occurrence of the Greek letter Alpha: Index 3
//       First occurrence of the Greek letter Omega: Index 0
using System;

class Example
{
   static void Main()
   {
      // Create a Unicode string with 5 Greek Alpha characters.
      String szGreekAlpha = new String('\u0391',5);

      // Create a Unicode string with 3 Greek Omega characters.
      String szGreekOmega = "\u03A9\u03A9\u03A9";
      
      String szGreekLetters = String.Concat(szGreekOmega, szGreekAlpha, 
                                            szGreekOmega.Clone());

      // Display the entire string.
      Console.WriteLine("The string: {0}", szGreekLetters);

      // The first index of Alpha.
      int ialpha = szGreekLetters.IndexOf('\u0391');
      // The first index of Omega.
      int iomega = szGreekLetters.IndexOf('\u03A9');

      Console.WriteLine("First occurrence of the Greek letter Alpha: Index {0}", 
                        ialpha);
      Console.WriteLine("First occurrence of the Greek letter Omega: Index {0}", 
                        iomega);
   }
} 
// The example displays the following output:
//    The string: OOO?????OOO
//    First occurrence of the Greek letter Alpha: Index 3
//    First occurrence of the Greek letter Omega: Index 0
Public Module Example
   Public Sub Main()
      ' Create a Unicode string with 5 Greek Alpha characters.
      Dim szGreekAlpha As New String(ChrW(&H0391), 5)

      ' Create a Unicode string with 3 Greek Omega characters.
      Dim szGreekOmega As String = ChrW(&H03A9) + ChrW(&H03A9)+
                                   ChrW(&H03A9)

      Dim szGreekLetters As String = String.Concat(szGreekOmega, szGreekAlpha, _
                                                   szGreekOmega.Clone())

      ' Display the entire string.
      Console.WriteLine(szGreekLetters)

      ' The first index of Alpha.
      Dim iAlpha As Integer = szGreekLetters.IndexOf(ChrW(&H0391))
      ' The first index of Omega.
      Dim iomega As Integer = szGreekLetters.IndexOf(ChrW(&H03A9))

      Console.WriteLine("First occurrence of the Greek letter Alpha: Index {0}", 
                        ialpha)
      Console.WriteLine("First occurrence of the Greek letter Omega: Index {0}", 
                        iomega)
   End Sub
End Module
' The example displays the following output:
'       The string: OOO?????OOO
'       First occurrence of the Greek letter Alpha: Index 3
'       First occurrence of the Greek letter Omega: Index 0

Commenti

Numerazione dell'indice inizia da zero.Index numbering starts from zero.

Questo metodo esegue una ricerca ordinale (cultura), in cui un carattere viene considerato equivalente a un altro solo se i relativi valori scalari Unicode sono uguali.This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. Per eseguire una ricerca dipendente dalle impostazioni cultura, usare il CompareInfo.IndexOf metodo, in cui un valore scalare Unicode che rappresenta un carattere precomposto, ad esempio la legatura "" (U + 00 C 6), potrebbe essere considerato equivalente a tutte le occorrenze di componenti del carattere di correggere sequenza, ad esempio quello "AE" (u+0041, U + 0045), in base alle impostazioni cultura.To perform a culture-sensitive search, use the CompareInfo.IndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature "Æ" (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.

Vedi anche

IndexOf(String, Int32) IndexOf(String, Int32) IndexOf(String, Int32) IndexOf(String, Int32)

Restituisce l'indice in base zero della prima occorrenza della stringa specificata in questa istanza.Reports the zero-based index of the first occurrence of the specified string in this instance. La ricerca ha inizio alla posizione del carattere specificata.The search starts at a specified character position.

public:
 int IndexOf(System::String ^ value, int startIndex);
public int IndexOf (string value, int startIndex);
member this.IndexOf : string * int -> int
Public Function IndexOf (value As String, startIndex As Integer) As Integer

Parametri

value
String String String String

Stringa da cercare.The string to seek.

startIndex
Int32 Int32 Int32 Int32

Posizione iniziale della ricerca.The search starting position.

Restituisce

Posizione dell'indice in base zero di value dall'inizio dell'istanza corrente se la stringa viene trovata oppure -1 in caso contrario.The zero-based index position of value from the start of the current instance if that string is found, or -1 if it is not. Se value è Empty, il valore restituito è startIndex.If value is Empty, the return value is startIndex.

Eccezioni

startIndex è minore di 0 (zero) o maggiore della lunghezza della stringa.is less than 0 (zero) or greater than the length of this string.

Esempi

Nell'esempio seguente esegue la ricerca di tutte le occorrenze di una stringa specificata all'interno di una stringa di destinazione.The following example searches for all occurrences of a specified string within a target string.

using namespace System;
int main()
{
   String^ strSource = "This is the string which we will perform the search on";
   Console::WriteLine( "The search string is: {0}\"{1}\" {0}", Environment::NewLine, strSource );
   String^ strTarget = "";
   int found = 0;
   int totFinds = 0;
   do
   {
      Console::Write( "Please enter a search value to look for in the above string (hit Enter to exit) ==> " );
      strTarget = Console::ReadLine();
      if (  !strTarget->Equals( "" ) )
      {
         for ( int i = 0; i < strSource->Length; i++ )
         {
            found = strSource->IndexOf( strTarget, i );
            if (found >= 0)
            {
               totFinds++;
               i = found;
            }
            else
               break;

         }
      }
      else
            return 0;
      Console::WriteLine( "{0}The search parameter '{1}' was found {2} times. {0}", Environment::NewLine, strTarget, totFinds );
      totFinds = 0;
   }
   while ( true );
}

using System;

public class IndexOfTest {
    public static void Main() {

        string strSource = "This is the string which we will perform the search on";

        Console.WriteLine("The search string is:{0}\"{1}\"{0}", Environment.NewLine, strSource);

        string strTarget = "";
        int found = 0;
        int totFinds = 0;

        do {
            Console.Write("Please enter a search value to look for in the above string (hit Enter to exit) ==> ");

            strTarget = Console.ReadLine();

            if (strTarget != "") {

                for (int i = 0; i < strSource.Length; i++) {

                    found = strSource.IndexOf(strTarget, i);

                    if (found >= 0) {
                        totFinds++;
                        i = found;
                    }
                    else
                        break;
                }
            }
            else
                return;

            Console.WriteLine("{0}The search parameter '{1}' was found {2} times.{0}",
                    Environment.NewLine, strTarget, totFinds);

            totFinds = 0;

        } while ( true );
    }
}
Imports System

Public Class IndexOfTest
    
    Public Shared Sub Main()
        Dim strSource As String = "This is the string which we will perform the search on"
        
        Console.WriteLine("The search string is:{0}{1}{0}", Environment.NewLine, strSource)
        Dim strTarget As String = ""
        Dim found As Integer = 0
        Dim totFinds As Integer = 0
        
        Do
            Console.Write("Please enter a search value to look for in the above string (hit Enter to exit) ==> ")
            
            strTarget = Console.ReadLine()
            If strTarget <> "" Then
                Dim i As Integer
                
                
                For i = 0 To strSource.Length - 1
                    
                    found = strSource.IndexOf(strTarget, i)
                    If found >= 0 Then
                        
                        totFinds += 1
                        i = found
                    Else
                        Exit For
                    End If
                Next i
            Else
                Return
            
            End If
            Console.WriteLine("{0}The search parameter '{1}' was found {2} times.{0}", Environment.NewLine, strTarget, totFinds)
            
            totFinds = 0
        
        Loop While True
    End Sub 'Main
End Class 'IndexOfTest

Commenti

Numerazione dell'indice inizia da 0.Index numbering starts from 0. Il parametro startIndex può avere un valore compreso tra 0 e la lunghezza dell'istanza della stringa.The startIndex parameter can range from 0 to the length of the string instance. Se startIndex è uguale alla lunghezza dell'istanza di stringa, il metodo restituisce -1.If startIndex equals the length of the string instance, the method returns -1.

Questo metodo esegue una ricerca di word (maiuscole/minuscole e distinzione delle impostazioni cultura) usando le impostazioni cultura correnti.This method performs a word (case-sensitive and culture-sensitive) search using the current culture. La ricerca inizia in corrispondenza di startIndex carattere posizione di questa istanza e continua fino a quando l'ultima posizione di carattere.The search begins at the startIndex character position of this instance and continues until the last character position.

I set di caratteri includono caratteri ignorabili, ovvero caratteri che non sono considerati durante l'esecuzione di un confronto linguistico o dipendente dalle impostazioni cultura.Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In una ricerca dipendente dalle impostazioni cultura, se value contiene un carattere ignorabile, il risultato è equivalente alla ricerca con il carattere rimosso.In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. Se value costituito solo da uno o più caratteri ignorabili, il IndexOf(String, Int32) metodo restituisce sempre startIndex, ovvero la posizione del carattere in corrispondenza del quale inizia la ricerca.If value consists only of one or more ignorable characters, the IndexOf(String, Int32) method always returns startIndex, which is the character position at which the search begins. Nell'esempio seguente, il IndexOf(String, Int32) metodo viene usato per trovare la posizione di un segno meno facoltativo (U + 00AD) seguita da una "m" in due stringhe.In the following example, the IndexOf(String, Int32) method is used to find the position of a soft hyphen (U+00AD) followed by an "m" in two strings. Solo una delle stringhe contiene la sottostringa richiesta.Only one of the strings contains the required substring. Se nell'esempio viene eseguito nel .NET Framework 4.NET Framework 4 o in un secondo momento, in entrambi i casi, poiché il segno meno facoltativo è un carattere ignorabile, il metodo restituisce l'indice di "m" nella stringa.If the example is run on the .NET Framework 4.NET Framework 4 or later, in both cases, because the soft hyphen is an ignorable character, the method returns the index of "m" in the string. Si noti che nel caso della prima stringa, che include il segno meno facoltativo seguito da una "m", il metodo non restituisce l'indice del segno meno facoltativo, ma l'indice di "m".Note that in the case of the first string, which includes the soft hyphen followed by an "m", the method fails to return the index of the soft hyphen but instead returns the index of the "m".

using System;

public class Example
{
   public static void Main()
   {
      string searchString = "\u00ADm";
      string s1 = "ani\u00ADmal" ;
      string s2 = "animal";

      Console.WriteLine(s1.IndexOf(searchString, 2));
      Console.WriteLine(s2.IndexOf(searchString, 2));
   }
}
// The example displays the following output:
//       4
//       3
Module Example
   Public Sub Main()
      Dim searchString As String = Chrw(&h00AD) + "m"
      Dim s1 As String = "ani" + ChrW(&h00AD) + "mal"
      Dim s2 As String = "animal"

      Console.WriteLine(s1.IndexOf(searchString, 2))
      Console.WriteLine(s2.IndexOf(searchString, 2))
   End Sub
End Module
' The example displays the following output:
'       4
'       3 

Note per i chiamanti

Come illustrato in Best Practices for Using Strings, è consigliabile evitare di chiamare i metodi di confronto tra stringhe che sostituiscono i valori predefiniti e invece chiamano metodi che richiedono parametri per specificare in modo esplicito.As explained in Best Practices for Using Strings, we recommend that you avoid calling string comparison methods that substitute default values and instead call methods that require parameters to be explicitly specified. Per trovare il primo indice di una sottostringa che si verifica dopo una posizione di carattere specifico usando le regole di confronto delle impostazioni cultura correnti, chiamare il IndexOf(String, Int32, StringComparison) overload del metodo con un valore di CurrentCulture per la relativa comparisonType parametro.To find the first index of a substring that occurs after a particular character position by using the comparison rules of the current culture, call the IndexOf(String, Int32, StringComparison) method overload with a value of CurrentCulture for its comparisonType parameter.

Vedi anche

Si applica a