IsNumber Method (String, Int32)
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Char.IsNumber Method (String, Int32)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

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 Shared Function IsNumber ( _
	s As String, _
	index As Integer _
) As Boolean


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 number; otherwise, false.


s is Nothing.


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

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

Dim surrogate As String = ChrW(&hD800) + ChrW(&hDD07)     ' AEGEAN NUMBER ONE
For ctr As Integer = 0 To surrogate.Length - 1
   outputBlock.Text += String.Format("U+{0:X4} at position {1}: {2}",  
                     Convert.ToUInt16(surrogate(ctr)), ctr,  
                     Char.IsNumber(surrogate, ctr)) + vbCrLf
' The example displays the following output:
'       U+D800 at position 0: True
'       U+DD07 at position 1: False

The following example demonstrates IsNumber.

Module Example

   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Dim str As String
      str = "non-numeric"

      outputBlock.Text &= Char.IsNumber("8"c) & vbCrLf      ' Output: "True"
      outputBlock.Text += String.Format(Char.IsNumber(str, 3)) & vbCrLf    ' Output: "False"

   End Sub

End Module

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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