Updated: December 2010
Indicates whether the character at the specified position in a specified string is categorized as a number.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function IsNumber ( _ s As String, _ index As Integer _ ) As Boolean
public static bool IsNumber( string s, int index )
public: static bool IsNumber( String^ s, int index )
static member IsNumber : s:string * index:int -> bool
Parameters
- s
- Type: System.String
A string.
- index
- Type: System.Int32
The position of the character to evaluate in s.
Return Value
Type: System.Booleantrue if the character at position index in s is a number; otherwise, false.
| Exception | Condition |
|---|---|
| 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 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 utf32 As Integer = &h10107 ' AEGEAN NUMBER ONE Dim surrogate As String = Char.ConvertFromUtf32(utf32) For ctr As Integer = 0 To surrogate.Length - 1 Console.WriteLine("U+{0:X4} at position {1}: {2}", Convert.ToUInt16(surrogate(ctr)), ctr, Char.IsNumber(surrogate, ctr)) Next ' The example displays the following output: ' U+D800 at position 0: True ' U+DD07 at position 1: 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.
Module IsNumberSample Sub Main() Dim str As String str = "non-numeric" Console.WriteLine(Char.IsNumber("8"c)) ' Output: "True" Console.WriteLine(Char.IsNumber(str, 3)) ' Output: "False" End Sub End Module
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" } }
using namespace System; int 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, 3.5, 3.0, 2.0, 1.1, 1.0.NET Framework Client Profile
Supported in: 4, 3.5 SP1Portable Class Library
Supported in: Portable Class LibraryWindows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Reference
|
Date |
History |
Reason |
|---|---|---|
|
December 2010 |
Added information about how the method handles surrogate pairs. |
Information enhancement. |