Char.IsNumber Method

Definition

Indicates whether a Unicode character is categorized as a number.

Overloads

IsNumber(Char)

Indicates whether the specified Unicode character is categorized as a number.

IsNumber(String, Int32)

Indicates whether the character at the specified position in a specified string is categorized as a number.

IsNumber(Char)

Source:
Char.cs
Source:
Char.cs
Source:
Char.cs

Indicates whether the specified Unicode character is categorized as a number.

public static bool IsNumber (char c);

Parameters

c
Char

The Unicode character to evaluate.

Returns

true if c is a number; otherwise, false.

Examples

The following example demonstrates IsNumber.

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"
    }
}

Remarks

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.

Important

The IsNumber(Char) method is not intended to determine whether a string consists of numeric characters (for example, by calling the method for each character in a string). To determine whether a string consists of numeric characters, call one of the overloads of the TryParse method (such as Int32.TryParse or Double.TryParse of an integral or floating point type.

Valid numbers are members of the UnicodeCategory.DecimalDigitNumber, UnicodeCategory.LetterNumber, or UnicodeCategory.OtherNumber category.

The IsNumber(Char) method assumes that c corresponds to a single linguistic character and checks whether that character represents a number. 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 IsNumber(Char) method returns false if it is passed either a high surrogate or a low surrogate of this character.

int utf32 = 0x10107;      // AEGEAN NUMBER ONE
string surrogate = Char.ConvertFromUtf32(utf32);
foreach (var ch in surrogate)
   Console.WriteLine("U+{0:X4}: {1}", Convert.ToUInt16(ch),
                                    Char.IsNumber(ch));

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

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0

IsNumber(String, Int32)

Source:
Char.cs
Source:
Char.cs
Source:
Char.cs

Indicates whether the character at the specified position in a specified string is categorized as a number.

public static bool IsNumber (string s, int index);

Parameters

s
String

A string.

index
Int32

The position of the character to evaluate in s.

Returns

true if the character at position index in s is a number; otherwise, false.

Exceptions

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

Examples

The following example demonstrates IsNumber.

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"
    }
}

Remarks

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.

Important

The IsNumber(String, Int32) method is not intended to determine whether a string consists of numeric characters (for example, by calling the method for each character in a string). To determine whether a string consists of numeric characters, call one of the overloads of the TryParse method (such as Int32.TryParse or Double.TryParse of an integral or floating point type.

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(String, Int32) 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(String, Int32) 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.

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

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0