String.LastIndexOf メソッド

定義

このインスタンス内で最後に出現する指定 Unicode 文字または文字列の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified Unicode character or string within this instance. このインスタンス内で文字または文字列が見つからない場合、このメソッドは -1 を返します。The method returns -1 if the character or string is not found in this instance.

オーバーロード

LastIndexOf(String, Int32, StringComparison)

指定した文字列が現在の String オブジェクト内で最後に見つかった 0 から始まる位置のインデックスをレポートします。Reports the zero-based index of the last occurrence of a specified string within the current String object. 検索は、指定された文字位置から開始され、文字列の先頭に向かって逆方向に進みます。The search starts at a specified character position and proceeds backward toward the beginning of the string. 指定した文字列を検索するときに実行する比較の種類をパラメーターで指定します。A parameter specifies the type of comparison to perform when searching for the specified string.

LastIndexOf(String, Int32, Int32)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance. 検索は指定された文字位置から開始し、文字列の開始に向かって後方に移動し、文字位置の指定された数だけ行われます。The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.

LastIndexOf(Char, Int32, Int32)

このインスタンス内の部分文字列で最後に出現する指定 Unicode 文字の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of the specified Unicode character in a substring within this instance. 検索は指定された文字位置から開始し、文字列の開始に向かって後方に移動し、文字位置の指定された数だけ行われます。The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.

LastIndexOf(String, StringComparison)

指定した文字列が現在の String オブジェクト内で最後に見つかった 0 から始まる位置のインデックスをレポートします。Reports the zero-based index of the last occurrence of a specified string within the current String object. 指定した文字列に使用する検索の種類をパラメーターで指定します。A parameter specifies the type of search to use for the specified string.

LastIndexOf(Char)

このインスタンス内で最後に出現する指定 Unicode 文字の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance.

LastIndexOf(Char, Int32)

このインスタンス内で最後に出現する指定 Unicode 文字の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance. 検索は、指定された文字位置から開始され、文字列の先頭に向かって逆方向に進みます。The search starts at a specified character position and proceeds backward toward the beginning of the string.

LastIndexOf(String)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance.

LastIndexOf(String, Int32, Int32, StringComparison)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance. 検索は指定された文字位置から開始し、文字列の開始に向かって後方に移動し、文字位置の指定された数だけ行われます。The search starts at a specified character position and proceeds backward toward the beginning of the string for the specified number of character positions. 指定した文字列を検索するときに実行する比較の種類をパラメーターで指定します。A parameter specifies the type of comparison to perform when searching for the specified string.

LastIndexOf(String, Int32)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance. 検索は、指定された文字位置から開始され、文字列の先頭に向かって逆方向に進みます。The search starts at a specified character position and proceeds backward toward the beginning of the string.

LastIndexOf(String, Int32, StringComparison)

指定した文字列が現在の String オブジェクト内で最後に見つかった 0 から始まる位置のインデックスをレポートします。Reports the zero-based index of the last occurrence of a specified string within the current String object. 検索は、指定された文字位置から開始され、文字列の先頭に向かって逆方向に進みます。The search starts at a specified character position and proceeds backward toward the beginning of the string. 指定した文字列を検索するときに実行する比較の種類をパラメーターで指定します。A parameter specifies the type of comparison to perform when searching for the specified string.

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

パラメーター

value
String

シークする文字列。The string to seek.

startIndex
Int32

検索が開始される位置。The search starting position. 検索は、このインスタンスの先頭に向かって startIndex から開始されます。The search proceeds from startIndex toward the beginning of this instance.

comparisonType
StringComparison

検索の規則を指定する列挙値の 1 つ。One of the enumeration values that specifies the rules for the search.

戻り値

その文字列が見つかった場合は、value パラメーターの 0 から始まる開始インデックス位置。見つからなかった場合、または現在のインスタンスが Empty と等しい場合は -1。The zero-based starting index position of the value parameter if that string is found, or -1 if it is not found or if the current instance equals Empty. valueEmpty の場合、戻り値は startIndex かこのインスタンスの最後のインデックス位置のいずれか小さい方です。If value is Empty, the return value is the smaller of startIndex and the last index position in this instance.

例外

valuenull です。value is null.

現在のインスタンスが Empty と等しくなく、startIndex が 0 未満であるか、または現在のインスタンスの長さを超えています。The current instance does not equal Empty, and startIndex is less than zero or greater than the length of the current instance.

- または --or- 現在のインスタンスが Empty と等しく、startIndex が -1 未満であるか、または 0 を超えています。The current instance equals Empty, and startIndex is less than -1 or greater than zero.

comparisonType は有効な StringComparison 値ではありません。comparisonType is not a valid StringComparison value.

次の例は、StringComparison 列挙体の異なる値を使用して、別の文字列内で最後に出現する文字列を検索する、LastIndexOf メソッドの3つのオーバーロードを示しています。The following example demonstrates three overloads of the LastIndexOf method that find the last occurrence of a string within another string using different values of the StringComparison enumeration.

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

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

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the last 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 StringComparsion. Specify the start 
// index and count. 

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

// Search using different values of StringComparsion. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(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 last 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.LastIndexOf(String, ..., StringComparison) methods.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the last 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 StringComparsion. Specify the start 
        ' index and count. 
        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. Specify the 
        ' start index. 
        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. 
        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub
End Class

'
'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 last 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
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

検索は startIndex 文字位置から開始され、value が見つかるか、または最初の文字位置が検査されるまで、後方に進みます。The search begins at the startIndex character position and proceeds backward until either value is found or the first character position has been examined. たとえば、startIndex が-1 Length の場合、メソッドは文字列の最後の文字から先頭までのすべての文字を検索します。For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning.

comparisonType パラメーターは、大文字と小文字を区別するか、大文字と小文字を区別しない検索を使用し、word または序数の比較規則を使用して、現在のカルチャまたはインバリアントカルチャを使用して value パラメーターを検索するように指定します。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.

注意 (呼び出し元)

文字セットには無視できる文字が含まれています。これらの文字は、言語またはカルチャに依存した比較を実行する際には考慮されません。Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. カルチャに依存する検索の場合 (つまり、comparisonTypeOrdinal または OrdinalIgnoreCase でない場合)、value に無視できる文字が含まれていると、その文字を削除して検索した場合と同じ結果になります。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. value が1つ以上の無視できる文字で構成されている場合、LastIndexOf(String, Int32, StringComparison) メソッドは常に startIndexを返します。これは、検索を開始する文字の位置です。If value consists only of one or more ignorable characters, the LastIndexOf(String, Int32, StringComparison) method always returns startIndex, which is the character position at which the search begins.

次の例では、LastIndexOf(String, Int32, StringComparison) メソッドを使用して、2つの文字列の最後の "m" から始まる "m" の後に、ソフトハイフン (U + 00AD) の位置を検索します。In the following example, the LastIndexOf(String, Int32, StringComparison) method is used to find the position of a soft hyphen (U+00AD) followed by an "m", starting with the final "m" in two strings. 文字列の 1 つのみに必要な部分文字列が含まれます。Only one of the strings contains the required substring. この例が .NET Framework 4.NET Framework 4 以降で実行されている場合、どちらの場合も、ソフトハイフンが無視できない文字であるため、メソッドはカルチャに依存した比較を実行するときに、文字列内の "m" のインデックスを返します。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. "m" の後にソフト ハイフンが含まれる最初の文字列の場合、メソッドはソフト ハイフンのインデックスを返すことができず、代わりに "m" のインデックスを返すことに注意してください。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". このメソッドは、序数に基づく比較を実行したときのみ、最初の文字列に含まれるソフト ハイフンのインデックスを返します。The method returns the index of the soft hyphen in the first string only when it performs an ordinal comparison.

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

LastIndexOf(String, Int32, Int32)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance. 検索は指定された文字位置から開始し、文字列の開始に向かって後方に移動し、文字位置の指定された数だけ行われます。The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.

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

パラメーター

value
String

シークする文字列。The string to seek.

startIndex
Int32

検索が開始される位置。The search starting position. 検索は、このインスタンスの先頭に向かって startIndex から開始されます。The search proceeds from startIndex toward the beginning of this instance.

count
Int32

検査する文字位置の数。The number of character positions to examine.

戻り値

その文字列が見つかった場合は、value の 0 から始まる開始インデックス位置。見つからなかった場合、または現在のインスタンスが Empty と等しい場合は -1。The zero-based starting index position of value if that string is found, or -1 if it is not found or if the current instance equals Empty. valueEmpty の場合、戻り値は startIndex かこのインスタンスの最後のインデックス位置のいずれか小さい方です。If value is Empty, the return value is the smaller of startIndex and the last index position in this instance.

例外

valuenullです。value is null.

count が負の値です。count is negative.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex が負の値です。The current instance does not equal Empty, and startIndex is negative.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex がこのインスタンスの長さより大きいです。The current instance does not equal Empty, and startIndex is greater than the length of this instance.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex - count + 1 した値がこのインスタンス内にはない位置を指定しています。The current instance does not equal Empty, and startIndex - count+ 1 specifies a position that is not within this instance.

- または --or- 現在のインスタンスが Empty と等しく、start が -1 より小さいか 0 より大きいです。The current instance equals Empty and start is less than -1 or greater than zero.

- または --or- 現在のインスタンスが Empty と等しく、count が 1 より大きいです。The current instance equals Empty and count is greater than 1.

次の例では、部分文字列の末尾から部分文字列の先頭までの文字列の、部分文字列のすべての出現箇所のインデックスを検索します。The following example finds the index of all occurrences of a string in substring, working from the end of the substring to the start of the substring.

// Sample for String::LastIndexOf(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 count;
   int end;
   start = str->Length - 1;
   end = start / 2 - 1;
   Console::WriteLine( "All occurrences of 'he' from position {0} to {1}.", start, end );
   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 > -1) && (at > -1) )
   {
      count = start - end; //Count must be within the substring.
      at = str->LastIndexOf( "he", start, count );
      if ( at > -1 )
      {
         Console::Write( "{0} ", at );
         start = at - 1;
      }
   }

   Console::Write( "{0} {0} {0}", Environment::NewLine );
}

/*
This example produces the following results:
All occurrences of 'he' from position 66 to 32.
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): 56 45
*/
// Sample for String.LastIndexOf(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 count;
    int end;

    start = str.Length-1;
    end = start/2 - 1;
    Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, end);
    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 > -1) && (at > -1))
        {
        count = start - end; //Count must be within the substring.
        at = str.LastIndexOf("he", start, count);
        if (at > -1) 
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 'he' from position 66 to 32.
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): 56 45
*/
' Sample for String.LastIndexOf(String, Int32, Int32)
 _

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 count As Integer
      Dim [end] As Integer

      start = str.Length - 1
      [end] = start / 2 - 1
      Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, [end])
      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 > - 1 And at > - 1
         count = start - [end] 'Count must be within the substring.
         at = str.LastIndexOf("he", start, count)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 'he' from position 66 to 32.
'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): 56 45
'
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

検索は、このインスタンスの startIndex 文字位置から開始し、value が見つかるか、または count 文字位置が確認されるまで、先頭に向かって逆方向に進みます。The search begins at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or count character positions have been examined. たとえば、startIndex が-1 Length の場合、メソッドは文字列の最後の文字から後方 count 文字を検索します。For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string.

このメソッドは、現在のカルチャを使用して、単語 (大文字と小文字を区別し、カルチャに依存する) 検索を実行します。This method performs a word (case-sensitive and culture-sensitive) search using the current culture.

文字セットには無視できる文字が含まれています。これらの文字は、言語またはカルチャに依存した比較を実行する際には考慮されません。Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. カルチャに依存した検索では、value に無視できる文字が含まれている場合、その文字を削除して検索した場合と同じ結果になります。In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. value が1つ以上の無視できる文字で構成されている場合、LastIndexOf メソッドは常に startIndexを返します。これは、検索を開始する文字の位置です。If value consists only of one or more ignorable characters, the LastIndexOf method always returns startIndex, which is the character position at which the search begins. 次の例では、2つの文字列の最後の "m" の前にある2つの文字で、ソフトハイフン (U + 00AD) の位置を検索するために、LastIndexOf メソッドを使用しています。In the following example, the LastIndexOf method is used to find the position of a soft hyphen (U+00AD) in the two characters that precede the final "m" of two strings. 文字列の 1 つのみに必要な部分文字列が含まれます。Only one of the strings contains the required substring. この例が .NET Framework 4.NET Framework 4 以降で実行されている場合、どちらの場合も、ソフトハイフンが無視できない文字であるため、メソッドはカルチャに依存した比較を実行するときに、文字列内の "m" のインデックスを返します。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. "m" の後にソフト ハイフンが含まれる最初の文字列の場合、メソッドはソフト ハイフンのインデックスを返すことができず、代わりに "m" のインデックスを返すことに注意してください。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()
   {
      int position = 0;
      string s1 = "ani\u00ADmal";
      string s2 = "animal";
      
      // Find the index of the soft hyphen.
      position = s1.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)
         Console.WriteLine(s1.LastIndexOf("\u00AD", position, position + 1));

      position = s2.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)   
         Console.WriteLine(s2.LastIndexOf("\u00AD", position, position + 1));
      
      // Find the index of the soft hyphen followed by "n".
      position = s1.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)
         Console.WriteLine(s1.LastIndexOf("\u00ADn", position, position + 1));

      position = s2.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)   
         Console.WriteLine(s2.LastIndexOf("\u00ADn", position, position + 1));
      
      // Find the index of the soft hyphen followed by "m".
      position = s1.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)
         Console.WriteLine(s1.LastIndexOf("\u00ADm", position, position + 1));

      position = s2.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)   
         Console.WriteLine(s2.LastIndexOf("\u00ADm", position, position + 1));
   }
}
// The example displays the following output:
//       'm' at position 4
//       4
//       'm' at position 3
//       3
//       'm' at position 4
//       1
//       'm' at position 3
//       1
//       'm' at position 4
//       4
//       'm' at position 3
//       3
Module Example
   Public Sub Main()
      Dim position As Integer
      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.
      position = s1.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s1.LastIndexOf(softHyphen, position, position + 1))
      End If
         
      position = s2.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s2.LastIndexOf(softHyphen, position, position + 1))
      End If
      
      ' Find the index of the soft hyphen followed by "n".
      position = s1.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s1.LastIndexOf(softHyphen + "n", position, position + 1))
      End If
         
      position = s2.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s2.LastIndexOf(softHyphen + "n", position, position + 1))
      End If
      
      ' Find the index of the soft hyphen followed by "m".
      position = s1.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s1.LastIndexOf(softHyphen + "m", position, position + 1))
      End If
      
      position = s2.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s2.LastIndexOf(softHyphen + "m", position, position + 1))
      End If
   End Sub
End Module
' The example displays the following output:
'       'm' at position 4
'       4
'       'm' at position 3
'       3
'       'm' at position 4
'       1
'       'm' at position 3
'       1
'       'm' at position 4
'       4
'       'm' at position 3
'       3

注意 (呼び出し元)

文字列を使用するためのベストプラクティス」で説明したように、既定値を置き換える文字列比較メソッドを呼び出さずに、パラメーターを明示的に指定する必要があるメソッドを呼び出すことを避けることをお勧めします。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. 現在のカルチャの比較規則を使用してこの操作を実行するには、comparisonType パラメーターに CurrentCulture 値を指定して LastIndexOf(String, Int32, Int32, StringComparison) メソッドオーバーロードを呼び出します。To perform this operation by using the comparison rules of the current culture, call the LastIndexOf(String, Int32, Int32, StringComparison) method overload with a value of CurrentCulture for its comparisonType parameter.

こちらもご覧ください

LastIndexOf(Char, Int32, Int32)

このインスタンス内の部分文字列で最後に出現する指定 Unicode 文字の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of the specified Unicode character in a substring within this instance. 検索は指定された文字位置から開始し、文字列の開始に向かって後方に移動し、文字位置の指定された数だけ行われます。The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.

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

パラメーター

value
Char

シークする Unicode 文字。The Unicode character to seek.

startIndex
Int32

検索の開始位置。The starting position of the search. 検索は、このインスタンスの先頭に向かって startIndex から開始されます。The search proceeds from startIndex toward the beginning of this instance.

count
Int32

検査する文字位置の数。The number of character positions to examine.

戻り値

その文字が見つかった場合は、value の 0 から始まるインデックス位置。見つからなかった場合、または現在のインスタンスが Empty と等しい場合は -1。The zero-based index position of value if that character is found, or -1 if it is not found or if the current instance equals Empty.

例外

現在のインスタンスが Empty と等しくなく、startIndex が 0 未満であるか、このインスタンスの長さ以上です。The current instance does not equal Empty, and startIndex is less than zero or greater than or equal to the length of this instance.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex - count + 1 が 0 未満です。The current instance does not equal Empty, and startIndex - count + 1 is less than zero.

次の例では、部分文字列の末尾から部分文字列の先頭までの、部分文字列に出現するすべての文字のインデックスを検索します。The following example finds the index of all occurrences of a character in a substring, working from the end of the substring to the start of the substring.

// Sample for String::LastIndexOf(Char, 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 count;
   int end;
   start = str->Length - 1;
   end = start / 2 - 1;
   Console::WriteLine( "All occurrences of 't' from position {0} to {1}.", start, end );
   Console::WriteLine( "\n{0}\n{1}\n{2}", br1, br2, str );
   Console::Write( "The letter 't' occurs at position(s): " );
   count = 0;
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      count = start - end; //Count must be within the substring.
      at = str->LastIndexOf( 't', start, count );
      if ( at > -1 )
      {
         Console::Write( " {0} ", at );
         start = at - 1;
      }
   }
}

/*
This example produces the following results:
All occurrences of 't' from position 66 to 32.
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): 64 55 44 41 33


*/
// Sample for String.LastIndexOf(Char, 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 count;
    int end;

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

    count = 0;
    at = 0;
    while((start > -1) && (at > -1))
        {
        count = start - end; //Count must be within the substring.
        at = str.LastIndexOf('t', start, count);
        if (at > -1) 
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 't' from position 66 to 32.
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): 64 55 44 41 33


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

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 count As Integer
      Dim [end] As Integer

      start = str.Length - 1
      [end] = start / 2 - 1
      Console.WriteLine("All occurrences of 't' from position {0} to {1}.", start, [end])
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The letter 't' occurs at position(s): ")
      
      count = 0
      at = 0
      While start > - 1 And at > - 1
         count = start - [end] 'Count must be within the substring.
         at = str.LastIndexOf("t"c, start, count)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 't' from position 66 to 32.
'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): 64 55 44 41 33
'
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

このメソッドは、startIndex 文字位置から検索を開始し、value が見つかったか count 文字位置が検査されるまで、このインスタンスの先頭に向かって逆方向に進みます。This method begins searching at the startIndex character position and proceeds backward toward the beginning of this instance until either value is found or count character positions have been examined. たとえば、startIndex が-1 Length の場合、メソッドは文字列の最後の文字から後方 count 文字を検索します。For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string. 検索では大文字と小文字が区別されます。The search is case-sensitive.

このメソッドは、Unicode スカラー値が同じである場合にのみ、文字が別の文字と等価であると見なされる序数 (カルチャに依存しない) 検索を実行します。This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar value are the same. カルチャに依存した検索を実行するには、CompareInfo.LastIndexOf メソッドを使用します。このメソッドでは、合字 "Æ" (U + 00C6) など、構成されていない文字を表す Unicode スカラー値が、正しい文字のコンポーネントの出現箇所と等価であると見なされる場合があります。カルチャに応じた "AE" (U + 0041 という, U + 0045) などのシーケンス。To perform a culture-sensitive search, use the CompareInfo.LastIndexOf 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.

こちらもご覧ください

LastIndexOf(String, StringComparison)

指定した文字列が現在の String オブジェクト内で最後に見つかった 0 から始まる位置のインデックスをレポートします。Reports the zero-based index of the last occurrence of a specified string within the current String object. 指定した文字列に使用する検索の種類をパラメーターで指定します。A parameter specifies the type of search to use for the specified string.

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

パラメーター

value
String

シークする文字列。The string to seek.

comparisonType
StringComparison

検索の規則を指定する列挙値の 1 つ。One of the enumeration values that specifies the rules for the search.

戻り値

その文字列が見つかった場合は、value パラメーターの 0 から始まる開始インデックス位置。見つからなかった場合は -1。The zero-based starting index position of the value parameter if that string is found, or -1 if it is not. valueEmpty の場合、戻り値はこのインスタンスの最後のインデックス位置です。If value is Empty, the return value is the last index position in this instance.

例外

valuenullです。value is null.

comparisonType は有効な StringComparison 値ではありません。comparisonType is not a valid StringComparison value.

次の例は、StringComparison 列挙体の異なる値を使用して、別の文字列内で最後に出現する文字列を検索する、LastIndexOf メソッドの3つのオーバーロードを示しています。The following example demonstrates three overloads of the LastIndexOf method that find the last occurrence of a string within another string using different values of the StringComparison enumeration.

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

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

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the last 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 StringComparsion. Specify the start 
// index and count. 

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

// Search using different values of StringComparsion. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(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 last 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.LastIndexOf(String, ..., StringComparison) methods.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the last 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 StringComparsion. Specify the start 
        ' index and count. 
        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. Specify the 
        ' start index. 
        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. 
        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub
End Class

'
'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 last 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
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

comparisonType パラメーターは、大文字と小文字を区別するか、大文字と小文字を区別しない検索を使用し、word または序数の比較規則を使用して、現在のカルチャまたはインバリアントカルチャを使用して value パラメーターを検索するように指定します。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.

検索は、このインスタンスの最後の文字位置から開始し、value が見つかるか、または最初の文字位置が確認されるまで、先頭に向かって逆方向に進みます。The search begins at the last character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined.

注意 (呼び出し元)

文字セットには無視できる文字が含まれています。これらの文字は、言語またはカルチャに依存した比較を実行する際には考慮されません。Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. カルチャに依存する検索の場合 (つまり、optionsOrdinal または OrdinalIgnoreCase でない場合)、value に無視できる文字が含まれていると、その文字を削除して検索した場合と同じ結果になります。In a culture-sensitive search (that is, if options is not Ordinal or OrdinalIgnoreCase), if value contains an ignorable character, the result is equivalent to searching with that character removed. value が1つ以上の無視できる文字で構成されている場合、LastIndexOf(String, StringComparison) メソッドは常に、現在のインスタンスの最後のインデックス位置を表す Length-1 を返します。If value consists only of one or more ignorable characters, the LastIndexOf(String, StringComparison) method always returns Length - 1, which represents the last index position in the current instance.

次の例では、LastIndexOf(String, StringComparison) メソッドを使用して、2つの文字列の3つの部分文字列 (ソフトハイフン (U + 00AD)、ソフトハイフンの後に "n"、ソフトハイフンの後に "m") を検索します。In the following example, the LastIndexOf(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. 文字列の 1 つのみにソフト ハイフンが含まれます。Only one of the strings contains a soft hyphen. この例が .NET Framework 4.NET Framework 4 以降で実行されている場合は、ソフトハイフンが無視できる文字であるため、カルチャに依存した検索では、検索文字列にソフトハイフンが含まれていない場合に返されるのと同じ値が返されます。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. ただし、序数検索では、1つの文字列でソフトハイフンが正常に検出され、2番目の文字列に存在しないことが報告されます。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.LastIndexOf#26] [!code-vbSystem.String.LastIndexOf#26][!code-csharpSystem.String.LastIndexOf#26] [!code-vbSystem.String.LastIndexOf#26]

LastIndexOf(Char)

このインスタンス内で最後に出現する指定 Unicode 文字の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance.

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

パラメーター

value
Char

シークする Unicode 文字。The Unicode character to seek.

戻り値

その文字が見つかった場合は、value の 0 から始まるインデックスでの位置。見つからなかった場合は -1。The zero-based index position of value if that character is found, or -1 if it is not.

次の例では、LastIndexOf(Char) メソッドを使用して文字列内の最後のディレクトリ区切り文字を検索し、文字列のファイル名を抽出する ExtractFilename メソッドを定義しています。The following example defines an ExtractFilename method that uses the LastIndexOf(Char) method to find the last directory separator character in a string and to extract the string's file name. ファイルが存在する場合、メソッドはパスを指定せずにファイル名を返します。If the file exists, the method returns the file name without its path.

using System;
using System.IO;

public class TestLastIndexOf
{
   public static void Main()
   {
      string filename;
      
      filename = ExtractFilename(@"C:\temp\");
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);
      
      filename = ExtractFilename(@"C:\temp\delegate.txt"); 
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);

      filename = ExtractFilename("delegate.txt");      
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);
      
      filename = ExtractFilename(@"C:\temp\notafile.txt");
      Console.WriteLine("{0}", String.IsNullOrEmpty(filename) ? "<none>" : filename);
   }

   public static string ExtractFilename(string filepath)
   {
      // If path ends with a "\", it's a path only so return String.Empty.
      if (filepath.Trim().EndsWith(@"\"))
         return String.Empty;
      
      // Determine where last backslash is.
      int position = filepath.LastIndexOf('\\');
      // If there is no backslash, assume that this is a filename.
      if (position == -1)
      {
         // Determine whether file exists in the current directory.
         if (File.Exists(Environment.CurrentDirectory + Path.DirectorySeparatorChar + filepath)) 
            return filepath;
         else
            return String.Empty;
      }
      else
      {
         // Determine whether file exists using filepath.
         if (File.Exists(filepath))
            // Return filename without file path.
            return filepath.Substring(position + 1);
         else
            return String.Empty;
      }
   }
}
Imports System.IO

Public Module Test
   Public Sub Main()
      Dim filename As String 
      
      filename = ExtractFilename("C:\temp\")
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))
      
      filename = ExtractFilename("C:\temp\delegate.txt") 
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))

      filename = ExtractFilename("delegate.txt")      
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))
      
      filename = ExtractFilename("C:\temp\notafile.txt")
      Console.WriteLine("{0}", IIf(String.IsNullOrEmpty(fileName), "<none>", filename))
   End Sub
   
   Public Function ExtractFilename(filepath As String) As String
      ' If path ends with a "\", it's a path only so return String.Empty.
      If filepath.Trim().EndsWith("\") Then Return String.Empty
      
      ' Determine where last backslash is.
      Dim position As Integer = filepath.LastIndexOf("\"c)
      ' If there is no backslash, assume that this is a filename.
      If position = -1 Then
         ' Determine whether file exists in the current directory.
         If File.Exists(Environment.CurrentDirectory + Path.DirectorySeparatorChar + filepath) Then
            Return filepath
         Else
            Return String.Empty
         End If
      Else
         ' Determine whether file exists using filepath.
         If File.Exists(filepath) Then
            ' Return filename without file path.
            Return filepath.Substring(position + 1)
         Else
            Return String.Empty
         End If                     
      End If
   End Function
End Module 
' The example displays the following output:
'        delegate.txt

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

このメソッドは、このインスタンスの最後の文字位置から検索を開始し、value が見つかるか、または最初の文字位置が検査されるまで、先頭に向かって逆方向に進みます。This method begins searching at the last character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined. 検索では大文字と小文字が区別されます。The search is case-sensitive.

このメソッドは、Unicode スカラー値が同じである場合にのみ、文字が別の文字と等価であると見なされる序数 (カルチャに依存しない) 検索を実行します。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. カルチャに依存した検索を実行するには、CompareInfo.LastIndexOf メソッドを使用します。このメソッドでは、合字 "Æ" (U + 00C6) など、構成されていない文字を表す Unicode スカラー値が、正しい文字のコンポーネントの出現箇所と等価であると見なされる場合があります。カルチャに応じた "AE" (U + 0041 という, U + 0045) などのシーケンス。To perform a culture-sensitive search, use the CompareInfo.LastIndexOf 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.

こちらもご覧ください

LastIndexOf(Char, Int32)

このインスタンス内で最後に出現する指定 Unicode 文字の 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance. 検索は、指定された文字位置から開始され、文字列の先頭に向かって逆方向に進みます。The search starts at a specified character position and proceeds backward toward the beginning of the string.

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

パラメーター

value
Char

シークする Unicode 文字。The Unicode character to seek.

startIndex
Int32

検索の開始位置。The starting position of the search. 検索は、このインスタンスの先頭に向かって startIndex から開始されます。The search proceeds from startIndex toward the beginning of this instance.

戻り値

その文字が見つかった場合は、value の 0 から始まるインデックス位置。見つからなかった場合、または現在のインスタンスが Empty と等しい場合は -1。The zero-based index position of value if that character is found, or -1 if it is not found or if the current instance equals Empty.

例外

現在のインスタンスが Empty と等しくなく、startIndex が 0 未満であるか、このインスタンスの長さ以上です。The current instance does not equal Empty, and startIndex is less than zero or greater than or equal to the length of this instance.

次の例では、文字列の末尾から文字列の先頭まで、文字列内のすべての文字が出現する位置のインデックスを検索します。The following example finds the index of all occurrences of a character in a string, working from the end of the string to the start of the string.

// Sample for String::LastIndexOf(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;
   start = str->Length - 1;
   Console::WriteLine( "All occurrences of 't' from position {0} to 0.", start );
   Console::WriteLine( "{0}\n{1}\n{2}\n", br1, br2, str );
   Console::Write( "The letter 't' occurs at position(s): " );
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      at = str->LastIndexOf( 't', start );
      if ( at > -1 )
      {
         Console::Write( " {0} ", at );
         start = at - 1;
      }
   }
}

/*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
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): 64 55 44 41 33 11 7
*/
// Sample for String.LastIndexOf(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;

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

    at = 0;
    while((start > -1) && (at > -1))
        {
        at = str.LastIndexOf('t', start);
        if (at > -1) 
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 't' from position 66 to 0.
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): 64 55 44 41 33 11 7
*/
' Sample for String.LastIndexOf(Char, 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
      
      start = str.Length - 1
      Console.WriteLine("All occurrences of 't' from position {0} to 0.", start)
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The letter 't' occurs at position(s): ")
      
      at = 0
      While start > - 1 And at > - 1
         at = str.LastIndexOf("t"c, start)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 't' from position 66 to 0.
'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): 64 55 44 41 33 11 7
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字がインデックス0になり、最後の文字が Length-1 になります。このメソッドは、このインスタンスの startIndex 文字位置から検索を開始し、value が見つかるか、または最初の文字位置が検査されるまで、現在のインスタンスの先頭に向かって後方に移動します。That is, the first character in the string is at index zero and the last is at Length - 1.This method begins searching at the startIndex character position of this instance and proceeds backward toward the beginning of the current instance until either value is found or the first character position has been examined. たとえば、startIndex が-1 Length の場合、メソッドは文字列の最後の文字から先頭までのすべての文字を検索します。For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning. 検索では大文字と小文字が区別されます。The search is case-sensitive.

このメソッドは、Unicode スカラー値が同じである場合にのみ、文字が別の文字と等価であると見なされる序数 (カルチャに依存しない) 検索を実行します。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. カルチャに依存した検索を実行するには、CompareInfo.LastIndexOf メソッドを使用します。このメソッドでは、合字 "Æ" (U + 00C6) など、構成されていない文字を表す Unicode スカラー値が、正しい文字のコンポーネントの出現箇所と等価であると見なされる場合があります。カルチャに応じた "AE" (U + 0041 という, U + 0045) などのシーケンス。To perform a culture-sensitive search, use the CompareInfo.LastIndexOf 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.

こちらもご覧ください

LastIndexOf(String)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance.

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

パラメーター

value
String

シークする文字列。The string to seek.

戻り値

その文字列が見つかった場合は、value の 0 から始まる開始インデックス位置。見つからなかった場合は -1。The zero-based starting index position of value if that string is found, or -1 if it is not. valueEmpty の場合、戻り値はこのインスタンスの最後のインデックス位置です。If value is Empty, the return value is the last index position in this instance.

例外

valuenull です。value is null.

次の例では、タグが文字列の先頭と末尾にある場合に、HTML タグの開始と終了を文字列から削除します。The following example removes opening and closing HTML tags from a string if the tags begin and end the string. 文字列が右角かっこの文字 (">") で終わる場合、この例では、LastIndexOf メソッドを使用して終了タグの先頭を検索します。If a string ends with a closing bracket character (">"), the example uses the LastIndexOf method to locate the start of the end tag.

using System;

public class Example 
{
   public static void Main() 
   {
      string[] strSource = { "<b>This is bold text</b>", "<H1>This is large Text</H1>",
               "<b><i><font color=green>This has multiple tags</font></i></b>",
               "<b>This has <i>embedded</i> tags.</b>",
               "This line ends with a greater than symbol and should not be modified>" };

      // Strip HTML start and end tags from each string if they are present.
      foreach (string s in strSource)
      {
         Console.WriteLine("Before: " + s);
         string item = s;
         // Use EndsWith to find a tag at the end of the line.
         if (item.Trim().EndsWith(">")) 
         {
            // Locate the opening tag.
            int endTagStartPosition = item.LastIndexOf("</");
            // Remove the identified section, if it is valid.
            if (endTagStartPosition >= 0 )
               item = item.Substring(0, endTagStartPosition);

            // Use StartsWith to find the opening tag.
            if (item.Trim().StartsWith("<"))
            {
               // Locate the end of opening tab.
               int openTagEndPosition = item.IndexOf(">");
               // Remove the identified section, if it is valid.
               if (openTagEndPosition >= 0)
                  item = item.Substring(openTagEndPosition + 1);
            }      
         }
         // Display the trimmed string.
         Console.WriteLine("After: " + item);
         Console.WriteLine();
      }                   
   }
}
// The example displays the following output:
//    Before: <b>This is bold text</b>
//    After: This is bold text
//    
//    Before: <H1>This is large Text</H1>
//    After: This is large Text
//    
//    Before: <b><i><font color=green>This has multiple tags</font></i></b>
//    After: <i><font color=green>This has multiple tags</font></i>
//    
//    Before: <b>This has <i>embedded</i> tags.</b>
//    After: This has <i>embedded</i> tags.
//    
//    Before: This line ends with a greater than symbol and should not be modified>
//    After: This line ends with a greater than symbol and should not be modified>
Module Example
   Public Sub Main()
      Dim strSource As String() = { "<b>This is bold text</b>", _
                    "<H1>This is large Text</H1>", _
                    "<b><i><font color=green>This has multiple tags</font></i></b>", _
                    "<b>This has <i>embedded</i> tags.</b>", _
                    "This line ends with a greater than symbol and should not be modified>" }

      ' Strip HTML start and end tags from each string if they are present.
      For Each s As String In strSource
         Console.WriteLine("Before: " + s)
         ' Use EndsWith to find a tag at the end of the line.
         If s.Trim().EndsWith(">") Then 
            ' Locate the opening tag.
            Dim endTagStartPosition As Integer = s.LastIndexOf("</")
            ' Remove the identified section if it is valid.
            If endTagStartPosition >= 0 Then
               s = s.Substring(0, endTagStartPosition)
            End If
            
            ' Use StartsWith to find the opening tag.
            If s.Trim().StartsWith("<") Then
               ' Locate the end of opening tab.
               Dim openTagEndPosition As Integer = s.IndexOf(">")
               ' Remove the identified section if it is valid.
               If openTagEndPosition >= 0 Then
                  s = s.Substring(openTagEndPosition + 1)
               End If   
            End If      
         End If
         ' Display the trimmed string.
         Console.WriteLine("After: " + s)
         Console.WriteLine()
      Next                   
   End Sub
End Module
' The example displays the following output:
'    Before: <b>This is bold text</b>
'    After: This is bold text
'    
'    Before: <H1>This is large Text</H1>
'    After: This is large Text
'    
'    Before: <b><i><font color=green>This has multiple tags</font></i></b>
'    After: <i><font color=green>This has multiple tags</font></i>
'    
'    Before: <b>This has <i>embedded</i> tags.</b>
'    After: This has <i>embedded</i> tags.
'    
'    Before: This line ends with a greater than symbol and should not be modified>
'    After: This line ends with a greater than symbol and should not be modified>

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

検索は、このインスタンスの最後の文字位置から開始し、value が見つかるか、または最初の文字位置が確認されるまで、先頭に向かって逆方向に進みます。The search begins at the last character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined.

このメソッドは、現在のカルチャを使用して、単語 (大文字と小文字を区別し、カルチャに依存する) 検索を実行します。This method performs a word (case-sensitive and culture-sensitive) search using the current culture.

文字セットには無視できる文字が含まれています。これらの文字は、言語またはカルチャに依存した比較を実行する際には考慮されません。Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. カルチャに依存した検索では、value に無視できる文字が含まれている場合、その文字を削除して検索した場合と同じ結果になります。In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. value が1つ以上の無視できる文字で構成されている場合、LastIndexOf(String) メソッドは常に、現在のインスタンスの最後のインデックス位置を表す String.Length-1 を返します。If value consists only of one or more ignorable characters, the LastIndexOf(String) method always returns String.Length - 1, which represents the last index position in the current instance. 次の例では、LastIndexOf(String) メソッドを使用して、2つの文字列の3つの部分文字列 (ソフトハイフン (U + 00AD)、ソフトハイフンの後に "n"、ソフトハイフンの後に "m") を検索します。In the following example, the LastIndexOf(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. 文字列の 1 つのみにソフト ハイフンが含まれます。Only one of the strings contains a soft hyphen. この例が .NET Framework 4.NET Framework 4 以降で実行されている場合、ソフトハイフンが無視できない文字であるため、結果は valueにソフトハイフンが含まれていなかった場合と同じになります。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. ソフトハイフンのみを検索する場合、メソッドは6と5を返します。When searching for a soft hyphen only, the method returns 6 and 5. これらの値は、2つの文字列の最後の文字のインデックスに対応します。These values correspond to the index of the last character in the two strings.

using System;

public class Example
{
   public static void Main()
   {
      string s1 = "ani\u00ADmal";
      string s2 = "animal";
      
      // Find the index of the last soft hyphen.
      Console.WriteLine(s1.LastIndexOf("\u00AD"));
      Console.WriteLine(s2.LastIndexOf("\u00AD"));
      
      // Find the index of the last soft hyphen followed by "n".
      Console.WriteLine(s1.LastIndexOf("\u00ADn"));
      Console.WriteLine(s2.LastIndexOf("\u00ADn"));
      
      // Find the index of the last soft hyphen followed by "m".
      Console.WriteLine(s1.LastIndexOf("\u00ADm"));
      Console.WriteLine(s2.LastIndexOf("\u00ADm"));
   }
}
// The example displays the following output:
//       6
//       5
//       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 last soft hyphen.
      Console.WriteLine(s1.LastIndexOf(softHyphen))
      Console.WriteLine(s2.LastIndexOf(softHyphen))
      
      ' Find the index of the last soft hyphen followed by "n".
      Console.WriteLine(s1.LastIndexOf(softHyphen + "n"))
      Console.WriteLine(s2.LastIndexOf(softHyphen + "n"))
      
      ' Find the index of the last soft hyphen followed by "m".
      Console.WriteLine(s1.LastIndexOf(softHyphen + "m"))
      Console.WriteLine(s2.LastIndexOf(softHyphen + "m"))
   End Sub
End Module
' The example displays the following output:
'       6
'       5
'       1
'       1
'       4
'       3

注意 (呼び出し元)

文字列を使用するためのベストプラクティス」で説明したように、既定値を置き換える文字列比較メソッドを呼び出さずに、パラメーターを明示的に指定する必要があるメソッドを呼び出すことを避けることをお勧めします。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. 現在のカルチャの比較規則を使用して、文字列インスタンス内の部分文字列の最後のインデックスを検索するには、comparisonType パラメーターに CurrentCulture 値を指定して LastIndexOf(String, StringComparison) メソッドオーバーロードを呼び出します。To find the last index of a substring within a string instance by using the comparison rules of the current culture, call the LastIndexOf(String, StringComparison) method overload with a value of CurrentCulture for its comparisonType parameter.

こちらもご覧ください

LastIndexOf(String, Int32, Int32, StringComparison)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance. 検索は指定された文字位置から開始し、文字列の開始に向かって後方に移動し、文字位置の指定された数だけ行われます。The search starts at a specified character position and proceeds backward toward the beginning of the string for the specified number of character positions. 指定した文字列を検索するときに実行する比較の種類をパラメーターで指定します。A parameter specifies the type of comparison to perform when searching for the specified string.

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

パラメーター

value
String

シークする文字列。The string to seek.

startIndex
Int32

検索が開始される位置。The search starting position. 検索は、このインスタンスの先頭に向かって startIndex から開始されます。The search proceeds from startIndex toward the beginning of this instance.

count
Int32

検査する文字位置の数。The number of character positions to examine.

comparisonType
StringComparison

検索の規則を指定する列挙値の 1 つ。One of the enumeration values that specifies the rules for the search.

戻り値

その文字列が見つかった場合は、value パラメーターの 0 から始まる開始インデックス位置。見つからなかった場合、または現在のインスタンスが Empty と等しい場合は -1。The zero-based starting index position of the value parameter if that string is found, or -1 if it is not found or if the current instance equals Empty. valueEmpty の場合、戻り値は startIndex かこのインスタンスの最後のインデックス位置のいずれか小さい方です。If value is Empty, the return value is the smaller of startIndex and the last index position in this instance.

例外

valuenull です。value is null.

count が負の値です。count is negative.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex が負の値です。The current instance does not equal Empty, and startIndex is negative.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex がこのインスタンスの長さより大きいです。The current instance does not equal Empty, and startIndex is greater than the length of this instance.

- または --or- 現在のインスタンスが Empty と等しくなく、startIndex + 1 - count した値がこのインスタンス内にはない位置を指定しています。The current instance does not equal Empty, and startIndex + 1 - count specifies a position that is not within this instance.

- または --or- 現在のインスタンスが Empty と等しく、start が -1 より小さいか 0 より大きいです。The current instance equals Empty and start is less than -1 or greater than zero.

- または --or- 現在のインスタンスが Empty と等しく、count が 1 より大きいです。The current instance equals Empty and count is greater than 1.

comparisonType は有効な StringComparison 値ではありません。comparisonType is not a valid StringComparison value.

次の例は、StringComparison 列挙体の異なる値を使用して、別の文字列内で最後に出現する文字列を検索する、LastIndexOf メソッドの3つのオーバーロードを示しています。The following example demonstrates three overloads of the LastIndexOf method that find the last occurrence of a string within another string using different values of the StringComparison enumeration.

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

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

class Sample 
{
    public static void Main() 
    {
    string intro = "Find the last 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 StringComparsion. Specify the start 
// index and count. 

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

// Search using different values of StringComparsion. Specify the 
// start index. 
    Console.WriteLine("\nPart 2: Start index is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(CapitalAWithRing, cat.Length-1, sc);
        Console.WriteLine(resultFmt, sc, loc);
        }

// Search using different values of StringComparsion. 
    Console.WriteLine("\nPart 3: Neither start index nor count is specified.");
    foreach (StringComparison sc in scValues)
        {
        loc = cat.LastIndexOf(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 last 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.LastIndexOf(String, ..., StringComparison) methods.

Imports System.Threading
Imports System.Globalization

Class Sample
    Public Shared Sub Main() 
        Dim intro As String = "Find the last 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 StringComparsion. Specify the start 
        ' index and count. 
        Console.WriteLine("Part 1: Start index and count are specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, cat.Length, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. Specify the 
        ' start index. 
        Console.WriteLine(vbCrLf & "Part 2: Start index is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, cat.Length - 1, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
        
        ' Search using different values of StringComparsion. 
        Console.WriteLine(vbCrLf & "Part 3: Neither start index nor count is specified.")
        For Each sc In  scValues
            loc = cat.LastIndexOf(CapitalAWithRing, sc)
            Console.WriteLine(resultFmt, sc, loc)
        Next sc
    
    End Sub
End Class

'
'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 last 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
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

検索は startIndex 文字位置から開始され、value が見つかるか、または count 文字位置が調べられるまで、後方に進みます。The search begins at the startIndex character position and proceeds backward until either value is found or count character positions have been examined. たとえば、startIndex が-1 Length の場合、メソッドは文字列の最後の文字から後方 count 文字を検索します。For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string.

comparisonType パラメーターは、大文字と小文字を区別するか、大文字と小文字を区別しない検索を使用し、word または序数の比較規則を使用して、現在のカルチャまたはインバリアントカルチャを使用して value パラメーターを検索するように指定します。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.

注意 (呼び出し元)

文字セットには無視できる文字が含まれています。これらの文字は、言語またはカルチャに依存した比較を実行する際には考慮されません。Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. カルチャに依存する検索の場合 (つまり、comparisonTypeOrdinal または OrdinalIgnoreCase でない場合)、value に無視できる文字が含まれていると、その文字を削除して検索した場合と同じ結果になります。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. value が1つ以上の無視できる文字で構成されている場合、LastIndexOf(String, Int32, Int32, StringComparison) メソッドは常に startIndexを返します。これは、検索を開始する文字の位置です。If value consists only of one or more ignorable characters, the LastIndexOf(String, Int32, Int32, StringComparison) method always returns startIndex, which is the character position at which the search begins.

次の例では、LastIndexOf(String, Int32, Int32, StringComparison) メソッドを使用して、2つの文字列の最後の "m" の前にある最初の文字位置を除いて、ソフトハイフン (U + 00AD) の位置を検索します。In the following example, the LastIndexOf(String, Int32, Int32, StringComparison) method is used to find the position of a soft hyphen (U+00AD) followed by an "m" in all but the first character position before the final "m" in two strings. 文字列の 1 つのみに必要な部分文字列が含まれます。Only one of the strings contains the required substring. この例が .NET Framework 4.NET Framework 4 以降で実行されている場合、どちらの場合も、ソフトハイフンが無視できない文字であるため、メソッドはカルチャに依存した比較を実行するときに、文字列内の "m" のインデックスを返します。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. ただし、序数による比較を実行する場合は、最初の文字列でのみ部分文字列が検索されます。When it performs an ordinal comparison, however, it finds the substring only in the first string. ソフトハイフンの後に "m" が続く最初の文字列の場合、メソッドはソフトハイフンのインデックスを返すのではなく、カルチャに依存した比較を実行するときに "m" のインデックスを返すことに注意してください。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. このメソッドは、序数に基づく比較を実行したときのみ、最初の文字列に含まれるソフト ハイフンのインデックスを返します。The method returns the index of the soft hyphen in the first string only when it performs an ordinal comparison.

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

LastIndexOf(String, Int32)

指定された文字列がこのインスタンス内で最後に見つかった 0 から始まるインデックス位置をレポートします。Reports the zero-based index position of the last occurrence of a specified string within this instance. 検索は、指定された文字位置から開始され、文字列の先頭に向かって逆方向に進みます。The search starts at a specified character position and proceeds backward toward the beginning of the string.

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

パラメーター

value
String

シークする文字列。The string to seek.

startIndex
Int32

検索が開始される位置。The search starting position. 検索は、このインスタンスの先頭に向かって startIndex から開始されます。The search proceeds from startIndex toward the beginning of this instance.

戻り値

その文字列が見つかった場合は、value の 0 から始まる開始インデックス位置。見つからなかった場合、または現在のインスタンスが Empty と等しい場合は -1。The zero-based starting index position of value if that string is found, or -1 if it is not found or if the current instance equals Empty. valueEmpty の場合、戻り値は startIndex かこのインスタンスの最後のインデックス位置のいずれか小さい方です。If value is Empty, the return value is the smaller of startIndex and the last index position in this instance.

例外

valuenull です。value is null.

現在のインスタンスが Empty と等しくなく、startIndex が 0 未満であるか、または現在のインスタンスの長さを超えています。The current instance does not equal Empty, and startIndex is less than zero or greater than the length of the current instance.

- または --or- 現在のインスタンスが Empty と等しく、startIndex が -1 未満であるか、または 0 を超えています。The current instance equals Empty, and startIndex is less than -1 or greater than zero.

次の例では、ターゲット文字列内のすべての文字列のインデックスを検索し、ターゲット文字列の末尾からターゲット文字列の先頭に向かっています。The following example finds the index of all occurrences of a string in target string, working from the end of the target string to the start of the target string.

// Sample for String::LastIndexOf(String, 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;
   start = str->Length - 1;
   Console::WriteLine( "All occurrences of 'he' from position {0} to 0.", start );
   Console::WriteLine( "{0}\n{1}\n{2}\n", br1, br2, str );
   Console::Write( "The string 'he' occurs at position(s): " );
   at = 0;
   while ( (start > -1) && (at > -1) )
   {
      at = str->LastIndexOf( "he", start );
      if ( at > -1 )
      {
         Console::Write( " {0} ", at );
         start = at - 1;
      }
   }

   Console::WriteLine();
}

/*
This example produces the following results:
All occurrences of 'he' from position 66 to 0.
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):  56  45  8
*/
// Sample for String.LastIndexOf(String, 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;

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

    at = 0;
    while((start > -1) && (at > -1))
        {
        at = str.LastIndexOf("he", start);
        if (at > -1) 
            {
            Console.Write("{0} ", at);
            start = at - 1;
            }
        }
    Console.Write("{0}{0}{0}", Environment.NewLine);
    }
}
/*
This example produces the following results:
All occurrences of 'he' from position 66 to 0.
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): 56 45 8


*/
' Sample for String.LastIndexOf(String, Int32)
 _

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

      '#3
      start = str.Length - 1
      Console.WriteLine("All occurrences of 'he' from position {0} to 0.", start)
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The string 'he' occurs at position(s): ")
      
      at = 0
      While start > - 1 And at > - 1
         at = str.LastIndexOf("he", start)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub
End Class
'
'This example produces the following results:
'All occurrences of 'he' from position 66 to 0.
'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): 56 45 8
'
'

注釈

インデックス番号は0から始まります。Index numbering starts from zero. つまり、文字列の最初の文字はインデックス0になり、最後の文字は Length-1 になります。That is, the first character in the string is at index zero and the last is at Length - 1.

検索は、このインスタンスの startIndex 文字位置から開始し、value が見つかるか最初の文字位置が検査されるまで、先頭に向かって後方に移動します。The search begins at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined. たとえば、startIndex が-1 Length の場合、メソッドは文字列の最後の文字から先頭までのすべての文字を検索します。For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning.

このメソッドは、現在のカルチャを使用して、単語 (大文字と小文字を区別し、カルチャに依存する) 検索を実行します。This method performs a word (case-sensitive and culture-sensitive) search using the current culture.

文字セットには無視できる文字が含まれています。これらの文字は、言語またはカルチャに依存した比較を実行する際には考慮されません。Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. カルチャに依存した検索では、value に無視できる文字が含まれている場合、その文字を削除して検索した場合と同じ結果になります。In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. value が1つ以上の無視できる文字で構成されている場合、LastIndexOf(String, Int32) メソッドは常に startIndexを返します。これは、検索を開始する文字の位置です。If value consists only of one or more ignorable characters, the LastIndexOf(String, Int32) method always returns startIndex, which is the character position at which the search begins. 次の例では、LastIndexOf(String, Int32) メソッドを使用して、ソフトハイフン (U + 00AD) を含む部分文字列を検索し、最後の "m" を文字列の前または末尾に含めます。In the following example, the LastIndexOf(String, Int32) method is used to find a substring that includes a soft hyphen (U+00AD) and that precedes or includes the final "m" in a string. この例が .NET Framework 4.NET Framework 4 以降で実行される場合は、検索文字列のソフトハイフンが無視されるので、メソッドを呼び出して、ソフトハイフンで構成される部分文字列を検索し、"m" は文字列内の "m" の位置を返します。では、これを呼び出して、ソフトハイフンで構成される部分文字列を検索し、"n" は "n" の位置を返します。If the example is run on the .NET Framework 4.NET Framework 4 or later, because the soft hyphen in the search string is ignored, calling the method to find a substring that consists of the soft hyphen and "m" returns the position of the "m" in the string, whereas calling it to find a substring that consists of the soft hyphen and "n" returns the position of the "n". 検索文字列にソフトハイフンのみが含まれている場合、メソッドは、startIndexの値を表す "m" のインデックスを返します。When the search string contains only the soft hyphen, the method returns the index of the "m", which represents the value of startIndex.

using System;

public class Example
{
   public static void Main()
   {
      int position = 0;
      string s1 = "ani\u00ADmal";
      string s2 = "animal";
      
      // Find the index of the soft hyphen.
      position = s1.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)
         Console.WriteLine(s1.LastIndexOf("\u00AD", position));

      position = s2.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)   
         Console.WriteLine(s2.LastIndexOf("\u00AD", position));
      
      // Find the index of the soft hyphen followed by "n".
      position = s1.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)
         Console.WriteLine(s1.LastIndexOf("\u00ADn", position));

      position = s2.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)   
         Console.WriteLine(s2.LastIndexOf("\u00ADn", position));
      
      // Find the index of the soft hyphen followed by "m".
      position = s1.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)
         Console.WriteLine(s1.LastIndexOf("\u00ADm", position));

      position = s2.LastIndexOf("m");
      Console.WriteLine("'m' at position {0}", position);
      if (position >= 0)   
         Console.WriteLine(s2.LastIndexOf("\u00ADm", position));
   }
}
// The example displays the following output:
//       'm' at position 4
//       4
//       'm' at position 3
//       3
//       'm' at position 4
//       1
//       'm' at position 3
//       1
//       'm' at position 4
//       4
//       'm' at position 3
//       3
Module Example
   Public Sub Main()
      Dim position As Integer
      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.
      position = s1.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s1.LastIndexOf(softHyphen, position))
      End If
         
      position = s2.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s2.LastIndexOf(softHyphen, position))
      End If
      
      ' Find the index of the soft hyphen followed by "n".
      position = s1.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s1.LastIndexOf(softHyphen + "n", position))
      End If
         
      position = s2.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s2.LastIndexOf(softHyphen + "n", position))
      End If
      
      ' Find the index of the soft hyphen followed by "m".
      position = s1.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s1.LastIndexOf(softHyphen + "m", position))
      End If
      
      position = s2.LastIndexOf("m")
      Console.WriteLine("'m' at position {0}", position)
      If position >= 0 Then
         Console.WriteLine(s2.LastIndexOf(softHyphen + "m", position))
      End If
   End Sub
End Module
' The example displays the following output:
'       'm' at position 4
'       4
'       'm' at position 3
'       3
'       'm' at position 4
'       1
'       'm' at position 3
'       1
'       'm' at position 4
'       4
'       'm' at position 3
'       3

注意 (呼び出し元)

文字列を使用するためのベストプラクティス」で説明したように、既定値を置き換える文字列比較メソッドを呼び出さずに、パラメーターを明示的に指定する必要があるメソッドを呼び出すことを避けることをお勧めします。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. 現在のカルチャの比較規則を使用して特定の文字位置の前にある部分文字列のインデックスを検索するには、その comparisonType パラメーターに CurrentCulture の値を指定して、LastIndexOf(String, Int32, StringComparison) メソッドのオーバーロードを呼び出します。To find the index of a substring that precedes a particular character position by using the comparison rules of the current culture, call the LastIndexOf(String, Int32, StringComparison) method overload with a value of CurrentCulture for its comparisonType parameter.

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