String.TrimStart 方法

定义

命名空间:: System

程序集:: netstandard.dll, System.Runtime.dll

程序集:: mscorlib.dll, System.Runtime.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

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重载

名称	说明
TrimStart(Rune)
TrimStart(Char[])	从当前字符串中删除数组中指定的一组字符的所有前导匹配项。
TrimStart(Char)	从当前字符串中删除指定字符的所有前导匹配项。
TrimStart()	从当前字符串中删除所有前导空格字符。

TrimStart(Rune)

public:
 System::String ^ TrimStart(System::Text::Rune trimRune);

public string TrimStart(System.Text.Rune trimRune);

member this.TrimStart : System.Text.Rune -> string

Public Function TrimStart (trimRune As Rune) As String

参数

trimRune: Rune

String

适用于

TrimStart(Char[])

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

从当前字符串中删除数组中指定的一组字符的所有前导匹配项。

public:
 System::String ^ TrimStart(... cli::array <char> ^ trimChars);

public string TrimStart(params char[] trimChars);

public string TrimStart(params char[]? trimChars);

member this.TrimStart : char[] -> string

Public Function TrimStart (ParamArray trimChars As Char()) As String

参数

trimChars: Char[]

要删除的 Unicode 字符数组，或 null。

String

参数中 trimChars 所有字符出现后保留的字符串将从当前字符串的开头删除。如果 trimChars 为 null 空数组或空数组，则会删除空格字符。如果当前实例中无法剪裁任何字符，该方法将返回当前实例不变。

示例

以下示例演示了方法的基本功能 TrimStart ：

// 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

// TrimStart examples
let lineWithLeadingSpaces = "   Hello World!"
let lineWithLeadingSymbols = "$$$$Hello World!"
let lineWithLeadingUnderscores = "_____Hello World!"
let lineWithLeadingLetters = "xxxxHello World!"

// Make it easy to print out and work with all of the examples
let lines = [| lineWithLeadingSpaces; lineWithLeadingSymbols; lineWithLeadingUnderscores; lineWithLeadingLetters |]

for line in lines do
    printfn $"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
let lineAfterTrimStart = lineWithLeadingSpaces.TrimStart ' '
printfn $"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 lineToEdit in lines do
    printfn $"""{lineToEdit.TrimStart(' ', '$', '_', 'x')}"""
// Result for each: Hello World!

// or handle pieces of data that have multiple kinds of leading characters 
let lineToBeTrimmed = "__###__ John Smith"
let lineAfterTrimStart2 = lineToBeTrimmed.TrimStart('_', '#', ' ')
printfn $"{lineAfterTrimStart2}"
// 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

下面的示例使用此方法 TrimStart 从源代码行中剪裁空格和注释字符。该方法 StripComments 包装调用 TrimStart 并向其传递包含空格和注释字符的字符数组，该数组是 Visual Basic 中的撇号（'）和 C# 或 F# 中的斜杠（/）。 TrimStart在评估字符串是否为注释时，还调用该方法以删除前导空格。

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();
}

let stripComments (lines: #seq<string>) =
    [|  for line in lines do
            if line.TrimStart(' ').StartsWith "//" then
                line.TrimStart(' ', '/') |]

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

以下示例演示了对方法的 StripComments 调用。

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.

let lines = 
    [| "module HelloWorld"
       ""
       "[<EntryPoint>]"
       "let main _ ="
       "    // This code displays a simple greeting"
       "    // to the console."
       "    printfn \"Hello, World.\""
       "    0" |]
printfn "Before call to StripComments:"
for line in lines do
    printfn $"   {line}"

let strippedLines = stripComments lines
printfn "After call to StripComments:"
for line in strippedLines do
    printfn $"   {line}"
// This code produces the following output to the console:
//    Before call to StripComments:
//       module HelloWorld
//
//       [<EntryPoint>]
//       let main _ =
//           // This code displays a simple greeting
//           // to the console.
//           printfn "Hello, World."
//           0
//    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.

注解

该方法 TrimStart(System.Char[]) 从当前字符串中删除参数中的所有 trimChars 前导字符。当遇到未加入 trimChars 的字符时，剪裁作将停止。例如，如果当前字符串为“123abc456xyz789”，并且 trimChars 包含“1”到“9”的数字，则 TrimStart(System.Char[]) 该方法返回“abc456xyz789”。

注意

TrimStart(System.Char[])如果该方法从当前实例中删除任何字符，此方法不会修改当前实例的值。而是返回一个新字符串，其中删除了当前实例中找到 trimChars 的参数中的所有前导字符。

调用方说明

.NET Framework 3.5 SP1 和早期版本维护此方法剪裁的空白字符的内部列表（如果 trimChars 为 null 或空数组）。从 .NET Framework 4 开始，如果trimChars为null或为空数组，该方法将剪裁所有 Unicode 空格字符（也就是说，在传递给IsWhiteSpace(Char)方法时生成true返回值的字符）。由于此更改， Trim() .NET Framework 3.5 SP1 和早期版本中的方法删除了两个字符：零宽度空间（U+200B）和零宽度 NO-BREAK 空格（U+FEFF）， Trim() .NET Framework 4 及更高版本中的方法不会删除。此外， Trim() .NET Framework 3.5 SP1 和早期版本中的方法不会剪裁三个 Unicode 空格字符：MONGOLIAN VOWEL SEPARATOR（U+180E）、NARROW NO-BREAK SPACE（U+202F）和中等数学空间（U+205F）。

另请参阅

适用于

TrimStart(Char)

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

从当前字符串中删除指定字符的所有前导匹配项。

public:
 System::String ^ TrimStart(char trimChar);

public string TrimStart(char trimChar);

member this.TrimStart : char -> string

Public Function TrimStart (trimChar As Char) As String

参数

trimChar: Char

要删除的 Unicode 字符。

String

从当前字符串的开头删除所有匹配 trimChar 项之后保留的字符串。如果当前实例中无法剪裁任何字符，该方法将返回当前实例不变。

注解

该方法 TrimStart(System.Char) 从当前字符串中删除所有前导 trimChar 字符。当遇到未 trimChar 遇到字符时，剪裁作将停止。例如，如果 trimChar 为 - 当前字符串为“---abc---xyz----”，则 TrimStart(System.Char) 该方法返回“abc---xyz----”。

注意

TrimStart(System.Char)如果该方法从当前实例中删除任何字符，此方法不会修改当前实例的值。而是返回一个新字符串，在该字符串中删除当前实例中找到的所有前导 trimChar 字符。

适用于

TrimStart()

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

Source:: String.Manipulation.cs

从当前字符串中删除所有前导空格字符。

public:
 System::String ^ TrimStart();

public string TrimStart();

member this.TrimStart : unit -> string

Public Function TrimStart () As String

String

从当前字符串的开头删除所有空格字符之后保留的字符串。如果当前实例中无法剪裁任何字符，该方法将返回当前实例不变。

注解

该方法 TrimStart 从当前字符串中删除所有前导空格字符。遇到非空格字符时，剪裁操作将停止。例如，如果当前字符串为“abc xyz”，则 TrimStart 该方法返回“abc xyz”。

注意

TrimStart如果该方法从当前实例中删除任何字符，此方法不会修改当前实例的值。而是返回一个新字符串，在该字符串中删除当前实例中找到的所有前导空格字符。

适用于

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通过

String.TrimStart 方法

定义

重载

TrimStart(Rune)

参数

返回

适用于

TrimStart(Char[])

参数

返回

示例

注解

调用方说明

另请参阅

适用于

TrimStart(Char)

参数

返回

注解

适用于

TrimStart()

返回

注解

适用于

反馈