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Char.IsDigit Method (String, Int32)

Updated: October 2008

Indicates whether the character at the specified position in a specified string is categorized as a decimal digit.

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

public static bool IsDigit(
	string s,
	int index


Type: System.String

A String.

Type: System.Int32

The character position in s.

Return Value

Type: System.Boolean
true if the character at position index in s is a decimal digit; otherwise, false.


s is null.


index is less than zero or greater than the last position in s.

This method determines if a Char is a radix-10 digit. This contrasts with the IsNumber method, which determines if a Char is of any numeric Unicode category. Numbers include characters such as fractions, subscripts, superscripts, Roman numerals, currency numerators, encircled numbers, and script-specific digits.

Character positions in a string are indexed starting from zero.

Valid digits are members of the UnicodeCategory.DecimalDigitNumber category.

The following code example demonstrates IsDigit.

using System;

public class IsDigitSample {
	public static void Main() {
		char ch = '8';

		Console.WriteLine(Char.IsDigit(ch));					// Output: "True"
		Console.WriteLine(Char.IsDigit("sample string", 7));	// Output: "False"

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0




October 2008

Added detail about the difference between the IsDigit and IsNumber methods.

Customer feedback.