Char.GetNumericValue Method (Char)


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

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

Public Shared Function GetNumericValue (
	c As Char
) As Double


Type: System.Char

The Unicode character to convert.

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 uses the ConvertFromUtf32 method to instantiate a string that represents AEGEAN NUMBER ONE. As the output from the example shows, the GetNumericValue(Char) method returns -1 if it is passed either a high surrogate or a low surrogate of this character.

Dim utf32 As Integer = &h10107       ' AEGEAN NUMBER ONE
Dim surrogate As String = Char.ConvertFromUtf32(utf32)
For Each ch In surrogate
   Console.WriteLine("U+{0:X4}: {1}    ", Convert.ToUInt16(ch), 
' The example displays the following output:
'       U+D800: -1
'       U+DD07: -1

The following example demonstrates GetNumericValue.

Module GetNumericValueSample
    Sub Main()
        Dim str As String
        str = "input: 1"

        Console.WriteLine(Char.GetNumericValue("8"c))       ' Output: "8"
        Console.WriteLine(Char.GetNumericValue(str, 7))     ' Output: "1"
    End Sub
End Module

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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