String.TrimStart Method

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Overloads

TrimStart()	Removes all the leading white-space characters from the current string.
TrimStart(Char)	Removes all the leading occurrences of a specified character from the current string.
TrimStart(Char[])	Removes all the leading occurrences of a set of characters specified in an array from the current string.

TrimStart()

Source:

String.Manipulation.cs

Removes all the leading white-space characters from the current string.

public:
 System::String ^ TrimStart();

public string TrimStart ();

member this.TrimStart : unit -> string

Public Function TrimStart () As String

Returns

String

The string that remains after all white-space characters are removed from the start of the current string. If no characters can be trimmed from the current instance, the method returns the current instance unchanged.

Remarks

The TrimStart method removes from the current string all leading white-space characters. The trim operation stops when a non white-space character is encountered. For example, if the current string is " abc xyz ", the TrimStart method returns "abc xyz ".

Note

If the TrimStart method removes any characters from the current instance, this method does not modify the value of the current instance. Instead, it returns a new string in which all leading white space characters found in the current instance are removed.

TrimStart(Char)

Source:

String.Manipulation.cs

Removes all the leading occurrences of a specified character from the current string.

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

public string TrimStart (char trimChar);

member this.TrimStart : char -> string

Public Function TrimStart (trimChar As Char) As String

Parameters

trimChar

Char

The Unicode character to remove.

Returns

String

The string that remains after all occurrences of the trimChar character are removed from the start of the current string. If no characters can be trimmed from the current instance, the method returns the current instance unchanged.

Remarks

The TrimStart(System.Char) method removes from the current string all leading trimChar characters. The trim operation stops when a character that is not trimChar is encountered. For example, if trimChar is - and the current string is "---abc---xyz----", the TrimStart(System.Char) method returns "abc---xyz----".

Note

If the TrimStart(System.Char) method removes any characters from the current instance, this method does not modify the value of the current instance. Instead, it returns a new string in which all leading trimChar characters found in the current instance are removed.

TrimStart(Char[])

Source:

String.Manipulation.cs

Removes all the leading occurrences of a set of characters specified in an array from the current string.

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

Parameters

trimChars

Char[]

An array of Unicode characters to remove, or null.

Returns

String

The string that remains after all occurrences of characters in the trimChars parameter are removed from the start of the current string. If trimChars is null or an empty array, white-space characters are removed instead. If no characters can be trimmed from the current instance, the method returns the current instance unchanged.

Examples

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

// 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

The following example uses the TrimStart method to trim white space and comment characters from lines of source code. 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# or F#. 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();
}

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

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.

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.

Remarks

The TrimStart(System.Char[]) method removes from the current string all leading characters that are in the trimChars parameter. The trim operation stops when a character that is not in trimChars is encountered. For example, if the current string is "123abc456xyz789" and trimChars contains the digits from "1" through "9", the TrimStart(System.Char[]) method returns "abc456xyz789".

Note

If the TrimStart(System.Char[]) method removes any characters from the current instance, this method does not modify the value of the current instance. Instead, it returns a new string in which all leading characters that are in the trimChars parameter found in the current instance are removed.

Notes to Callers

The .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. Starting with the .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). Because of this change, the Trim() method in the .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 and later versions does not remove. In addition, the Trim() method in the .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).

See also

• Char
• Trim(Char[])
• TrimEnd(Char[])
• IsWhiteSpace(Char)