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CharUnicodeInfo.GetNumericValue Method (Char)

Updated: December 2010

Gets the numeric value associated with the specified character.

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

public static double GetNumericValue(
	char ch
)

Parameters

ch
Type: System.Char
The Unicode character for which to get the numeric value.

Return Value

Type: System.Double
The numeric value associated with the specified character.
-or-
-1, if the specified character is not a numeric character.

This property applies only to numeric characters, which include fractions, subscripts, superscripts, Roman numerals, currency numerators, encircled numbers, and script-specific digits.

For more information on Unicode characters, see the Unicode Standard.

The GetNumericValue method assumes that ch 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 uses the ConvertFromUtf32 method to instantiate a string that represents AEGEAN NUMBER ONE. As the output from the example shows, the GetNumericValue method returns -1 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),
                     System.Globalization.CharUnicodeInfo.GetNumericValue(ch)) + "\n";

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


The following code example shows the values returned by each method for different types of characters.


using System;
using System.Globalization;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      outputBlock.Text += "                                        c  Num   Dig   Dec   UnicodeCategory" + "\n";

      outputBlock.Text += "U+0061 LATIN SMALL LETTER A            ";
      PrintProperties(outputBlock, 'a');

      outputBlock.Text += "U+0393 GREEK CAPITAL LETTER GAMMA      ";
      PrintProperties(outputBlock, '\u0393');

      outputBlock.Text += "U+0039 DIGIT NINE                      ";
      PrintProperties(outputBlock, '9');

      outputBlock.Text += "U+00B2 SUPERSCRIPT TWO                 ";
      PrintProperties(outputBlock, '\u00B2');

      outputBlock.Text += "U+00BC VULGAR FRACTION ONE QUARTER     ";
      PrintProperties(outputBlock, '\u00BC');

      outputBlock.Text += "U+0BEF TAMIL DIGIT NINE                ";
      PrintProperties(outputBlock, '\u0BEF');

      outputBlock.Text += "U+0BF0 TAMIL NUMBER TEN                ";
      PrintProperties(outputBlock, '\u0BF0');

      outputBlock.Text += "U+0F33 TIBETAN DIGIT HALF ZERO         ";
      PrintProperties(outputBlock, '\u0F33');

      outputBlock.Text += "U+2788 CIRCLED SANS-SERIF DIGIT NINE   ";
      PrintProperties(outputBlock, '\u2788');
   }

   public static void PrintProperties(System.Windows.Controls.TextBlock outputBlock, char c)
   {
      outputBlock.Text += String.Format(" {0,-3}", c);
      outputBlock.Text += String.Format(" {0,-5}", CharUnicodeInfo.GetNumericValue(c));
      outputBlock.Text += String.Format("{0}", CharUnicodeInfo.GetUnicodeCategory(c)) + "\n";
   }
}
/*
This example produces the following output. 
   U+0061 LATIN SMALL LETTER A             a   -1   LowercaseLetter
   U+0393 GREEK CAPITAL LETTER GAMMA       G   -1   UppercaseLetter
   U+0039 DIGIT NINE                       9   9    DecimalDigitNumber
   U+00B2 SUPERSCRIPT TWO                  ²   2    OtherNumber
   U+00BC VULGAR FRACTION ONE QUARTER      ¼   0.25 OtherNumber
   U+0BEF TAMIL DIGIT NINE                 ?  9    DecimalDigitNumber
   U+0BF0 TAMIL NUMBER TEN                 ?   10   OtherNumber
   U+0F33 TIBETAN DIGIT HALF ZERO          ? -0.5   OtherNumber
   U+2788 CIRCLED SANS-SERIF DIGIT NINE    ?    9   OtherNumber
*/


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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