Char.IsLetterOrDigit Method (Char) (System)

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.NET Framework Class Library

Char.IsLetterOrDigit Method (Char)

Indicates whether the specified Unicode character is categorized as a letter or a decimal digit.

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

Syntax

Visual Basic

Public Shared Function IsLetterOrDigit ( _
	c As Char _
) As Boolean

public static bool IsLetterOrDigit(
	char c
)

Visual C++

public:
static bool IsLetterOrDigit(
	wchar_t c
)

static member IsLetterOrDigit : 
        c:char -> bool

Parameters

c: Type: System.Char
The Unicode character to evaluate.

Return Value

Type: System.Boolean
true if c is a letter or a decimal digit; otherwise, false.

Remarks

Valid letters and decimal digits are members of the following categories in UnicodeCategory: UppercaseLetter, LowercaseLetter, TitlecaseLetter, ModifierLetter, OtherLetter, or DecimalDigitNumber.

Examples

The following code example demonstrates IsLetterOrDigit.

Visual Basic


imports System

Module IsLetterOrDigitSample

    Sub Main()

        Dim str As String
        str = "newline:" + vbNewLine

        Console.WriteLine(Char.IsLetterOrDigit("8"c))       ' Output: "True"
        Console.WriteLine(Char.IsLetterOrDigit(str, 8))     ' Output: "False", because it's a NewLine

    End Sub

End Module


using System;

public class IsLetterOrDigitSample {
	public static void Main() {
		string str = "newline:\n";

		Console.WriteLine(Char.IsLetterOrDigit('8'));		// Output: "True"
		Console.WriteLine(Char.IsLetterOrDigit(str, 8));	// Output: "False", because it's a newline
	}
}

Visual C++


using namespace System;
int main()
{
   String^ str =  "newline:\n";
   Console::WriteLine( Char::IsLetterOrDigit( '8' ) ); // Output: "True"
   Console::WriteLine( Char::IsLetterOrDigit( str, 8 ) ); // Output: "False", because it's a newline
}

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

Char Structure

IsLetterOrDigit Overload

System Namespace

Boolean

Community Content

Shital Shah

It's not just a-zA-Z0-9

Char.IsLetterOrDigit('Ѝ') returns true , because that's a letter in the Cyrillic alphabet

R Petrusha - MSFT

AM i Correct ?

imports System

Module IsLetterOrDigitSample

Sub Main()

Dim str AsString
str = "newline:" + vbNewLine

Console.WriteLine(Char.IsLetterOrDigit("8"c)) ' Output: "True"
Console.WriteLine(Char.IsLetterOrDigit(str, 8)) ' Output: "False", because it's a NewLine
'From Programista 'I think the colon (:) makes the output False.
EndSub

End Module

I'm not sure what you mean by "makes the output False". But you can modify the example somewhat to evaluate each character in a string:

Module IsLetterOrDigitSample
   Sub Main()
      Dim str As String        
      str = "newline:" + vbNewLine        

      For Each ch In str
         Console.WriteLine("'{0}' (0x{2:X4})': {1}", 
                           If(ch >= "!", ch, ""), 
                           Char.IsLetterOrDigit(ch), 
                           Convert.ToUInt16(ch))
      Next
   End Sub
End Module

This displays the following output:

'n' (0x006E)': True
'e' (0x0065)': True
'w' (0x0077)': True
'l' (0x006C)': True
'i' (0x0069)': True
'n' (0x006E)': True
'e' (0x0065)': True
':' (0x003A)': False
'' (0x000D)': False
'' (0x000A)': False

--Ron Petrusha
Common Language Runtime Developer Content
Microsoft Corporation