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Char.GetNumericValue Method (Char)

Updated: December 2010

Converts the specified numeric Unicode character to a double-precision floating point number.

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

public static double GetNumericValue(
	char c
)

Parameters

c
Type: System.Char
A Unicode character.

Return Value

Type: System.Double
The numeric value of c if that character represents a number; otherwise, -1.0.

The c parameter must be the Char representation of a numeric value. For example, if c is '5', the return value is 5. However, if c is 'z', the return value is -1.0.

A character has an associated numeric value if and only if it is a member of one of the following UnicodeCategory categories: DecimalDigitNumber, LetterNumber, or OtherNumber.

The GetNumericValue method assumes that c corresponds to a single linguistic character and checks whether that character can be converted to a decimal digit. However, some numbers in the Unicode standard are represented by two Char objects that form a surrogate pair. For example, the Aegean numbering system consists of code points U+10107 through U+10133. The following example instantiates a string that represents AEGEAN NUMBER ONE. As the output from the example shows, the GetNumericValue method returns false if it is passed either a high surrogate or a low surrogate of this character.


string surrogate = "\uD800\uDD07";            // AEGEAN NUMBER ONE
foreach (var ch in surrogate)
   outputBlock.Text += String.Format("U+{0:X4}: {1}    ", Convert.ToUInt16(ch),
                                          Char.GetNumericValue(ch)) + "\n";

// The example displays the following output:
//       U+D800: -1
//       U+DD07: -1


The following example demonstrates GetNumericValue.


using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string str = "input: 1";

      outputBlock.Text += Char.GetNumericValue('8') + "\n";        // Output: "8"
      outputBlock.Text += Char.GetNumericValue(str, 7) + "\n";     // Output: "1"
   }
}


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Date

History

Reason

December 2010

Added information about how the method handles surrogate pairs.

Information enhancement.

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