String.Trim Method (Char())


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Removes all leading and trailing occurrences of a set of characters specified in an array from the current String object.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

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


Type: System.Char()

An array of Unicode characters to remove, or null.

Return Value

Type: System.String

The string that remains after all occurrences of the characters in the trimChars parameter are removed from the start and end 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.

The Trim method removes from the current string all leading and trailing characters that are in the trimChars parameter. Each leading and trailing 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 Trim method returns "abc456xyz".


If the Trim 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 and trailing trimChars characters found in the current instance are removed.

If the current string equals Empty or all the characters in the current instance consist of characters in the trimChars array, the method returns Empty.

If trimChars is null or an empty array, this method removes any leading or trailing characters that result in the method returning true when they are passed to the Char.IsWhiteSpace method,

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 Char.IsWhiteSpace 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 4and 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).

The following example uses the String.Trim(Char()) method to remove space, asterisk (*), and apostrophe (') characters from a string.

Module Example
   Public Sub Main()
      Dim charsToTrim() As Char = { "*"c, " "c, "'"c}
      Dim banner As String = "*** Much Ado About Nothing ***"
      Dim result As String = banner.Trim(charsToTrim)
      Console.WriteLine("Trimmmed{0}   {1}{0}to{0}   '{2}'", _
                        vbCrLf, banner, result)
   End Sub
End Module
' The example displays the following output:
'       Trimmmed
'          *** Much Ado About Nothing ***
'       to
'          'Much Ado About Nothing'

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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