Char.IsNumber Method (String, Int32)

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

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

public static bool IsNumber(
	string s,
	int index
)

Parameters

s
Type: System.String

A string.

index
Type: System.Int32

The position of the character to evaluate in s.

Return Value

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

ExceptionCondition
ArgumentNullException

s is null.

ArgumentOutOfRangeException

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

This method determines whether a Char is of any numeric Unicode category. In addition to including digits, numbers include characters, fractions, subscripts, superscripts, Roman numerals, currency numerators, and encircled numbers. This method contrasts with the IsDigit method, which determines whether a Char is a radix-10 digit.

Character positions in a string are indexed starting from zero.

Valid numbers are members of the UnicodeCategory.DecimalDigitNumber, UnicodeCategory.LetterNumber, or UnicodeCategory.OtherNumber category.

If the Char object at position index is the first character of a valid surrogate pair, the IsNumber(String, Int32) method determines whether the surrogate pair forms a numeric digit. For example, the Aegean numbering system consists of code points U+10107 through U+10133. The following example uses the ConvertFromUtf32 method to instantiate a string that represents AEGEAN NUMBER ONE. As the output from the example shows, the IsNumber(String, Int32) method returns true if it is passed the high surrogate of AEGEAN NUMBER ONE. However, if it is passed the low surrogate, it considers only the category of the low surrogate and returns false.

int utf32 = 0x10107;      // AEGEAN NUMBER ONE 
string surrogate = Char.ConvertFromUtf32(utf32);
for (int ctr = 0; ctr < surrogate.Length; ctr++)
   Console.WriteLine("U+{0:X4} at position {1}: {2}", 
                     Convert.ToUInt16(surrogate[ctr]), ctr,  
                     Char.IsNumber(surrogate, ctr));
// The example displays the following output: 
//       U+D800 at position 0: True 
//       U+DD07 at position 1: False

The following example demonstrates IsNumber.

using System;

public class IsNumberSample {
	public static void Main() {
		string str = "non-numeric";

		Console.WriteLine(Char.IsNumber('8'));		// Output: "True"
		Console.WriteLine(Char.IsNumber(str, 3));	// Output: "False"
	}
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 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

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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