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

Définition

Surcharges

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

Supprime, de l'objet String actuel, toutes les occurrences situées au début d'un jeu de caractères spécifiés dans un tableau.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

Retours

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

Supprime, de l'objet String actuel, toutes les occurrences situées au début d'un jeu de caractères spécifiés dans un tableau.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

Paramètres

trimChars
Char[]

Tableau de caractères Unicode à supprimer, ou null.An array of Unicode characters to remove, or null.

Retours

Chaîne qui reste après la suppression de toutes les occurrences des caractères contenus dans le paramètre trimChars du début de la chaîne actuelle.The string that remains after all occurrences of characters in the trimChars parameter are removed from the start of the current string. Si trimChars est null ou est un tableau vide, les espaces blancs sont plutôt supprimés.If trimChars is null or an empty array, white-space characters are removed instead.

Exemples

L’exemple suivant illustre les fonctionnalités de base de TrimStart la méthode :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

L’exemple suivant utilise la TrimStart méthode pour supprimer les espaces blancs et les caractères de commentaire des lignes de code source.The following example uses the TrimStart method to trim white space and comment characters from lines of source code. La StripComments méthode encapsule un appel à TrimStart et lui passe un tableau de caractères qui contient un espace et le caractère de commentaire, qui est une apostrophe (') dans Visual Basic et une barre oblique ( C#/) dans.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#. La TrimStart méthode est également appelée pour supprimer l’espace blanc de début lorsque vous évaluez si une chaîne est un commentaire.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   

L’exemple suivant illustre un appel à la méthode 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.   

Remarques

La TrimStart méthode supprime de la chaîne actuelle tous les caractères de début qui se trimChars trouvent dans le paramètre.The TrimStart method removes from the current string all leading characters that are in the trimChars parameter. L’opération de suppression s’arrête lorsqu’un caractère qui n' trimChars est pas dans est rencontré.The trim operation stops when a character that is not in trimChars is encountered. Par exemple, si la chaîne actuelle est « 123abc456xyz789 » et trimChars contient les chiffres de « 1 » à « 9 », la TrimStart méthode retourne « abc456xyz789 ».For example, if the current string is "123abc456xyz789" and trimChars contains the digits from "1" through "9", the TrimStart method returns "abc456xyz789".

Notes

Si la TrimStart méthode supprime tous les caractères de l’instance actuelle, cette méthode ne modifie pas la valeur de l’instance actuelle.If the TrimStart method removes any characters from the current instance, this method does not modify the value of the current instance. Au lieu de cela, elle retourne une nouvelle chaîne dans laquelle tous les caractères d’espace blanc de début trouvés dans l’instance actuelle sont supprimés.Instead, it returns a new string in which all leading white space characters found in the current instance are removed.

Notes pour les appelants

Le .NET Framework 3.5 SP1.NET Framework 3.5 SP1 et les versions antérieures maintiennent une liste interne d’espaces blancs que cette méthode tronque si trimChars est null ou un tableau vide.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. À compter de .NET Framework 4.NET Framework 4, si trimChars est null ou un tableau vide, la méthode supprime tous les espaces blancs Unicode (autrement dit, les caractères qui produisent une true valeur de retour lorsqu’ils sont passés à la IsWhiteSpace(Char) méthode).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). En raison de cette modification, Trim() la méthode dans .NET Framework 3.5 SP1.NET Framework 3.5 SP1 le et les versions antérieures supprime deux caractères, l’espace de largeur zéro (u + 200B) et l’espace de non-saut de largeur zéro ( Trim() u + FEFF .NET Framework 4.NET Framework 4 ), que la méthode dans et versions ultérieures ne pas supprimer.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. En outre, la Trim() méthode dans et .NET Framework 3.5 SP1.NET Framework 3.5 SP1 les versions antérieures ne supprime pas trois espaces blancs Unicode : SÉPARATEUR de VOYELLEs mongole (U + 180E), espace insécable étroit (U + 202F) et espace mathématique moyen (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).

Voir aussi

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

Paramètres

trimChar
Char Char Char Char

Retours

S’applique à