String.TrimStart String.TrimStart String.TrimStart String.TrimStart Method

Definice

Přetížení

TrimStart() TrimStart() TrimStart() TrimStart()
TrimStart(Char[]) TrimStart(Char[]) TrimStart(Char[]) TrimStart(Char[])

Odebere všechny úvodní výskyty sady znaků zadané v poli z aktuálního String objektu.Removes all leading occurrences of a set of characters specified in an array from the current String object.

TrimStart(Char) TrimStart(Char) TrimStart(Char) TrimStart(Char)

TrimStart() TrimStart() TrimStart() TrimStart()

public:
 System::String ^ TrimStart();
public string TrimStart ();
member this.TrimStart : unit -> string
Public Function TrimStart () As String

Návraty

TrimStart(Char[]) TrimStart(Char[]) TrimStart(Char[]) TrimStart(Char[])

Odebere všechny úvodní výskyty sady znaků zadané v poli z aktuálního String objektu.Removes all leading occurrences of a set of characters specified in an array from the current String object.

public:
 System::String ^ TrimStart(... cli::array <char> ^ trimChars);
public string TrimStart (params char[] trimChars);
member this.TrimStart : char[] -> string
Public Function TrimStart (ParamArray trimChars As Char()) As String

Parametry

trimChars
Char[]

Pole znaků Unicode, které se má odebrat, nullnebo.An array of Unicode characters to remove, or null.

Návraty

Řetězec, který zůstane po všech výskytech znaků v trimChars parametru, je odebrán od začátku aktuálního řetězce.The string that remains after all occurrences of characters in the trimChars parameter are removed from the start of the current string. Pokud trimChars jenull nebo prázdné pole, místo toho se odeberou prázdné prázdné znaky.If trimChars is null or an empty array, white-space characters are removed instead.

Příklady

Následující příklad ukazuje základní funkce TrimStart metody:The following example demonstrates the basic functionality of the TrimStart method:

// TrimStart examples
string lineWithLeadingSpaces = "   Hello World!";
string lineWithLeadingSymbols = "$$$$Hello World!";
string lineWithLeadingUnderscores = "_____Hello World!";
string lineWithLeadingLetters = "xxxxHello World!";
string lineAfterTrimStart = string.Empty;

// Make it easy to print out and work with all of the examples
string[] lines = { lineWithLeadingSpaces, lineWithLeadingSymbols, lineWithLeadingUnderscores, lineWithLeadingLetters };

foreach (var line in lines)
{
    Console.WriteLine($"This line has leading characters: {line}");
}
// Output:
// This line has leading characters:    Hello World!
// This line has leading characters: $$$$Hello World!
// This line has leading characters: _____Hello World!
// This line has leading characters: xxxxHello World!

// A basic demonstration of TrimStart in action
lineAfterTrimStart = lineWithLeadingSpaces.TrimStart(' ');
Console.WriteLine($"This is the result after calling TrimStart: {lineAfterTrimStart}");
// This is the result after calling TrimStart: Hello World!   

// Since TrimStart accepts a character array of leading items to be removed as an argument,
// it's possible to do things like trim multiple pieces of data that each have different 
// leading characters,
foreach (var lineToEdit in lines)
{
    Console.WriteLine(lineToEdit.TrimStart(' ', '$', '_', 'x'));
}
// Result for each: Hello World!

// or handle pieces of data that have multiple kinds of leading characters 
var lineToBeTrimmed = "__###__ John Smith";
lineAfterTrimStart = lineToBeTrimmed.TrimStart('_', '#', ' ');
Console.WriteLine(lineAfterTrimStart);
// Result: John Smith
Public Sub Main()
   ' TrimStart Examples
   Dim lineWithLeadingSpaces as String = "   Hello World!"
   Dim lineWithLeadingSymbols as String = "$$$$Hello World!"
   Dim lineWithLeadingUnderscores as String = "_____Hello World!"
   Dim lineWithLeadingLetters as String = "xxxxHello World!"
   Dim lineAfterTrimStart = String.Empty

   ' Make it easy to print out and work with all of the examples
   Dim lines As String() = { lineWithLeadingSpaces, line lineWithLeadingSymbols, lineWithLeadingUnderscores, lineWithLeadingLetters }

   For Each line As String in lines
     Console.WriteLine($"This line has leading characters: {line}")
   Next
   ' Output:
   ' This line has leading characters:    Hello World!
   ' This line has leading characters: $$$$Hello World!
   ' This line has leading characters: _____Hello World!
   ' This line has leading characters: xxxxHello World!

   Console.WriteLine($"This line has leading spaces: {lineWithLeadingSpaces}")
   ' This line has leading spaces:   Hello World!

   ' A basic demonstration of TrimStart in action
   lineAfterTrimStart = lineWithLeadingSpaces.TrimStart(" "c)
   Console.WriteLine($"This is the result after calling TrimStart: {lineAfterTrimStart}")
   ' This is the result after calling TrimStart: Hello World!

   ' Since TrimStart accepts a character array of leading items to be removed as an argument,
   ' it's possible to do things like trim multiple pieces of data that each have different 
   ' leading characters,
   For Each lineToEdit As String in lines
     Console.WriteLine(lineToEdit.TrimStart(" "c, "$"c, "_"c, "x"c ))
   Next
   ' Result for each: Hello World!

   ' or handle pieces of data that have multiple kinds of leading characters
   Dim lineToBeTrimmed as String = "__###__ John Smith"
   lineAfterTrimStart = lineToBeTrimmed.TrimStart("_"c , "#"c , " "c)
   Console.WriteLine(lineAfterTrimStart)
   ' Result: John Smith

 End Sub

Následující příklad používá TrimStart metodu pro oříznutí mezer a znaků komentářů z řádků zdrojového kódu.The following example uses the TrimStart method to trim white space and comment characters from lines of source code. Metoda zabalí volání do TrimStart a předá ho pole znaků, které obsahuje mezeru a znak komentáře, který je apostrofem (') v Visual Basic a lomítkem (/) v. C# StripCommentsThe StripComments method wraps a call to TrimStart and passes it a character array that contains a space and the comment character, which is an apostrophe ( ' ) in Visual Basic and a slash ( / ) in C#. TrimStart Metoda je také volána pro odebrání počátečního prázdného místa při vyhodnocování, zda je řetězec komentář.The TrimStart method is also called to remove leading white space when evaluating whether a string is a comment.

public static string[] StripComments(string[] lines)
{
    List<string> lineList = new List<string>();
    foreach (string line in lines)
    {
        if (line.TrimStart(' ').StartsWith("//"))
            lineList.Add(line.TrimStart(' ', '/'));
    }
    return lineList.ToArray();
}
Public Shared Function StripComments(lines() As String) As String()
   Dim lineList As New List(Of String)
   For Each line As String In lines
      If line.TrimStart(" "c).StartsWith("'") Then
         linelist.Add(line.TrimStart("'"c, " "c))
      End If
   Next
   Return lineList.ToArray()
End Function   

Následující příklad ukazuje volání StripComments metody.The following example then illustrates a call to the StripComments method.

public static void Main()
{
    string[] lines = {"using System;",
                   "",
                   "public class HelloWorld",
                   "{",
                   "   public static void Main()",
                   "   {",
                   "      // This code displays a simple greeting",
                   "      // to the console.",
                   "      Console.WriteLine(\"Hello, World.\");",
                   "   }",
                   "}"};
    Console.WriteLine("Before call to StripComments:");
    foreach (string line in lines)
        Console.WriteLine("   {0}", line);

    string[] strippedLines = StripComments(lines);
    Console.WriteLine("After call to StripComments:");
    foreach (string line in strippedLines)
        Console.WriteLine("   {0}", line);
}
// This code produces the following output to the console:
//    Before call to StripComments:
//       using System;
//   
//       public class HelloWorld
//       {
//           public static void Main()
//           {
//               // This code displays a simple greeting
//               // to the console.
//               Console.WriteLine("Hello, World.");
//           }
//       }  
//    After call to StripComments:
//       This code displays a simple greeting
//       to the console.
Public Shared Sub Main()
   Dim lines() As String = {"Public Module HelloWorld", _
                            "   Public Sub Main()", _
                            "      ' This code displays a simple greeting", _
                            "      ' to the console.", _
                            "      Console.WriteLine(""Hello, World."")", _
                            "   End Sub", _
                            " End Module"}
   Console.WriteLine("Code before call to StripComments:")
   For Each line As String In lines
      Console.WriteLine("   {0}", line)                         
   Next                            
   
   Dim strippedLines() As String = StripComments(lines) 
   Console.WriteLine("Code after call to StripComments:")
   For Each line As String In strippedLines
      Console.WriteLine("   {0}", line)                         
   Next                            
End Sub
' This code produces the following output to the console:
'    Code before call to StripComments:
'       Public Module HelloWorld
'          Public Sub Main()
'             ' This code displays a simple greeting
'             ' to the console.
'             Console.WriteLine("Hello, World.")
'          End Sub
'       End Module
'    Code after call to StripComments:
'       This code displays a simple greeting
'       to the console.   

Poznámky

Metoda odebere z aktuálního řetězce všechny úvodní znaky, které jsou trimChars v parametru. TrimStartThe TrimStart method removes from the current string all leading characters that are in the trimChars parameter. Operace Trim se zastaví, když dojde k výskytu znaku trimChars , který není v.The trim operation stops when a character that is not in trimChars is encountered. Pokud je aktuální řetězec například "123abc456xyz789" a trimChars obsahuje číslice od "1" až "9" TrimStart , metoda vrátí "abc456xyz789".For example, if the current string is "123abc456xyz789" and trimChars contains the digits from "1" through "9", the TrimStart method returns "abc456xyz789".

Poznámka

TrimStart Pokud metoda odebere z aktuální instance všechny znaky, tato metoda neupraví hodnotu aktuální instance.If the TrimStart method removes any characters from the current instance, this method does not modify the value of the current instance. Místo toho vrátí nový řetězec, ve kterém jsou odebrány všechny úvodní prázdné znaky nalezené v aktuální instanci.Instead, it returns a new string in which all leading white space characters found in the current instance are removed.

Poznámky pro volající

A starší verze udržuje interní seznam prázdných znaků, který tato metoda ořízne, pokud trimChars je null nebo prázdné pole. .NET Framework 3.5 SP1.NET Framework 3.5 SP1The .NET Framework 3.5 SP1.NET Framework 3.5 SP1 and earlier versions maintains an internal list of white-space characters that this method trims if trimChars is null or an empty array. trimChars null true Počínaje parametrem .NET Framework 4.NET Framework 4, pokud je nebo prázdné pole, metoda ořízne všechny prázdné znaky Unicode (tj. znaky, které vyvolávají návratovou hodnotu, když jsou předány IsWhiteSpace(Char) metodě).Starting with the .NET Framework 4.NET Framework 4, if trimChars is null or an empty array, the method trims all Unicode white-space characters (that is, characters that produce a true return value when they are passed to the IsWhiteSpace(Char) method). Z důvodu této Trim() změny metoda .NET Framework 3.5 SP1.NET Framework 3.5 SP1 v a starších verzích odebere dva znaky, nulovou šířku (u + 200B) a nulovou šířku mezer (u + Trim() FEFF), .NET Framework 4.NET Framework 4 že metoda v a novějších verzích neodebírat.Because of this change, the Trim() method in the .NET Framework 3.5 SP1.NET Framework 3.5 SP1 and earlier versions removes two characters, ZERO WIDTH SPACE (U+200B) and ZERO WIDTH NO-BREAK SPACE (U+FEFF), that the Trim() method in the .NET Framework 4.NET Framework 4 and later versions does not remove. Kromě toho Trim() metoda .NET Framework 3.5 SP1.NET Framework 3.5 SP1 v a starších verzích neořízne tři prázdné znaky Unicode: MONGOLSKÁ čárka (U + 180E), ZÚŽENí prostoru bez mezer (U + 202F) a středního MATEMATICKÉho prostoru (U + 205F).In addition, the Trim() method in the .NET Framework 3.5 SP1.NET Framework 3.5 SP1 and earlier versions does not trim three Unicode white-space characters: MONGOLIAN VOWEL SEPARATOR (U+180E), NARROW NO-BREAK SPACE (U+202F), and MEDIUM MATHEMATICAL SPACE (U+205F).

Viz také

TrimStart(Char) TrimStart(Char) TrimStart(Char) TrimStart(Char)

public:
 System::String ^ TrimStart(char trimChar);
public string TrimStart (char trimChar);
member this.TrimStart : char -> string
Public Function TrimStart (trimChar As Char) As String

Parametry

trimChar
Char Char Char Char

Návraty

Platí pro