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| Title | Trim leading and trailing non-printing ASCII characters from a string in Visual Basic .NET |
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| Description | This example shows how to trim leading and trailing non-printing ASCII characters from a string in Visual Basic .NET. |
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| Keywords | trim, ltrim, rtrim, TrimWhitespace, LTrimWhitespace, RTrimWhitespace, non-printing, ASCII, carriage return, linefeed, line feed |
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| Categories | Strings, Tips and Tricks |
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The NonprintingChars function returns an array of all of the non-printing 1-byte ASCII characters. These come before " " and after "~".
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' Return a string containing all
' non-printing, 1-byte ASCII characters.
Private Function NonprintingChars() As Char()
Const ASC_SPACE As Integer = Asc(" ")
Const ASC_TILDE As Integer = Asc("~")
Const NUM_CHARS As Integer = ASC_SPACE + (255 - _
ASC_TILDE)
Static chars() As Char = Nothing
' Initialize chars.
If chars Is Nothing Then
ReDim chars(NUM_CHARS - 1)
Dim i As Integer
For i = 0 To ASC_SPACE - 1
chars(i) = Chr(i)
Next i
Dim next_index As Integer = ASC_SPACE
For i = ASC_TILDE + 1 To 255
chars(next_index) = Chr(i)
next_index += 1
Next i
End If
Return chars
End Function
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The LTrimWhitespace, RTrimWhitespace, and TrimWhitespace functions simply call the string's TrimStart, TrimEnd, and Trim functions, passing them the array of non-printing characters that should be trimmed off.
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' Remove leading ASCII characters before " " and after "~".
Private Function LTrimWhitespace(ByVal txt As String) As _
String
Return txt.TrimStart(NonprintingChars())
End Function
' Remove trailing ASCII characters before " " and after "~".
Private Function RTrimWhitespace(ByVal txt As String) As _
String
Return txt.TrimEnd(NonprintingChars())
End Function
' Remove leading and trailing ASCII characters before " "
' and after "~".
Private Function TrimWhitespace(ByVal txt As String) As _
String
Return txt.Trim(NonprintingChars())
End Function
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