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

Definição

Sobrecargas

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

Remove todas as ocorrências à esquerda de um conjunto de caracteres especificados em uma matriz do atual objeto String.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

Retornos

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

Remove todas as ocorrências à esquerda de um conjunto de caracteres especificados em uma matriz do atual objeto String.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

Parâmetros

trimChars
Char[]

Uma matriz de caracteres Unicode a ser removida, ou null.An array of Unicode characters to remove, or null.

Retornos

A cadeia de caracteres que permanece depois que todas as ocorrências de caracteres no parâmetro trimChars forem removidas do início da cadeia de caracteres atual.The string that remains after all occurrences of characters in the trimChars parameter are removed from the start of the current string. Se trimChars for null ou uma matriz vazia, os caracteres de espaço em branco serão removidos.If trimChars is null or an empty array, white-space characters are removed instead.

Exemplos

O exemplo a seguir demonstra a funcionalidade básica do TrimStart método:The following example demonstrates the basic functionality of the TrimStart method:

public static void Main(string[] args)
{
    // 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

O exemplo a seguir usa o TrimStart método Cortar espaços em branco e caracteres de comentário das linhas de código-fonte.The following example uses the TrimStart method to trim white space and comment characters from lines of source code. O StripComments método encapsula uma chamada para TrimStart e passa uma matriz de caracteres que contém um espaço e o caractere de comentário, que é um apóstrofo (') no Visual Basic e uma barra (/) em c#.The 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#. O TrimStart método também é chamado para remover o espaço em branco ao avaliar se uma cadeia de caracteres é um comentário.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   

O exemplo a seguir mostra uma chamada para o método StripComments.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.   

Comentários

O TrimStart método Remove da cadeia de caracteres atual, todos os caracteres à esquerda que estão no trimChars parâmetro.The TrimStart method removes from the current string all leading characters that are in the trimChars parameter. A operação de corte é interrompido quando um caractere que não esteja em trimChars for encontrado.The trim operation stops when a character that is not in trimChars is encountered. Por exemplo, se a cadeia de caracteres atual é "123abc456xyz789" e trimChars contém os dígitos de "1" a "9", o TrimStart método retorna "abc456xyz789".For example, if the current string is "123abc456xyz789" and trimChars contains the digits from "1" through "9", the TrimStart method returns "abc456xyz789".

Observação

Se o TrimStart método Remove todos os caracteres da instância atual, esse método não modifica o valor da instância atual.If the TrimStart method removes any characters from the current instance, this method does not modify the value of the current instance. Em vez disso, ele retorna uma nova cadeia de caracteres na qual todos os caracteres de espaço em branco à esquerda encontrados na instância atual são removidos.Instead, it returns a new string in which all leading white space characters found in the current instance are removed.

Notas aos Chamadores

O .NET Framework 3,5 SP1.NET Framework 3.5 SP1 e versões anteriores mantém uma lista interna de caracteres de espaço em branco que esse método corta se trimChars é null ou uma matriz vazia.The .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. Começando com o .NET Framework 4.NET Framework 4, se trimChars é null ou uma matriz vazia, o método Remove todos os caracteres de espaço em branco Unicode (isto é, os caracteres que produzem um true valor de retorno quando eles são passados para o IsWhiteSpace(Char) método).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). Por causa dessa alteração, o Trim() método na .NET Framework 3,5 SP1.NET Framework 3.5 SP1 e versões anteriores remove dois caracteres, o espaço de largura ZERO (U + 200B) e espaço sem quebra de largura ZERO (U + FEFF), que o Trim() método no .NET Framework 4.NET Framework 4 e versões posteriores não não remover.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. Além disso, o Trim() método no .NET Framework 3,5 SP1.NET Framework 3.5 SP1 e versões anteriores não apare três caracteres de espaço em branco Unicode: SEPARADOR de VOGAL MONGOL (U + 180E), espaço limitado de não-SEPARAÇÃO (U + 202F) e espaço de MATEMÁTICA de médio (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).

Veja também

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

Parâmetros

trimChar
Char Char Char Char

Retornos

Aplica-se a