Char.IsLetter Method

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Indicates whether a Unicode character is categorized as a Unicode letter.

Overloads

IsLetter(Char)	Indicates whether the specified Unicode character is categorized as a Unicode letter.
IsLetter(String, Int32)	Indicates whether the character at the specified position in a specified string is categorized as a Unicode letter.

Examples

The following code example demonstrates IsLetter.

using namespace System;
int main()
{
   char ch = '8';
   Console::WriteLine( Char::IsLetter( ch ) ); // False
   Console::WriteLine( Char::IsLetter(  "sample string", 7 ) ); // True
}

using System;

public class IsLetterSample {
    public static void Main() {
        char ch = '8';

        Console.WriteLine(Char.IsLetter(ch));					// False
        Console.WriteLine(Char.IsLetter("sample string", 7));	// True
    }
}

open System

let ch = '8'

printfn $"{Char.IsLetter ch}"                       // False
printfn $"""{Char.IsLetter("sample string", 7)}"""  // True

Module IsLetterSample

    Sub Main()

        Dim ch8 As Char
        ch8 = "8"c

        Console.WriteLine(Char.IsLetter(ch8))                   ' Output: "False"
        Console.WriteLine(Char.IsLetter("sample string", 5))    ' Output: "True"

    End Sub

End Module

Remarks

This method determines whether a Char is a member of any category of Unicode letter. Unicode letters include the following:

• Uppercase letters, such as U+0041 (LATIN CAPITAL LETTER A) through U+005A (LATIN CAPITAL LETTER Z), or U+0400 (CYRILLIC CAPITAL LETTER IE WITH GRAVE) through U+042F (CYRILLIC CAPITAL LETTER YA). These characters are members of the UnicodeCategory.UppercaseLetter category.

• Lowercase letters, such as U+0061 (LATIN SMALL LETTER A) through U+007A (LATIN SMALL LETTER Z), or U+03AC (GREEK SMALL LETTER ALPHA WITH TONOS) through U+03CE (GREEK SMALL LETTER OMEGA WITH TONOS). These characters are members of the UnicodeCategory.LowercaseLetter category.

• Title case letters, such as U+01C5 (LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON) or U+1FFC (GREEK CAPITAL LETTER OMEGA WITH PROSGEGRAMMENI). These characters are members of the UnicodeCategory.TitlecaseLetter category.

• Modifiers, such as U+02B0 (MODIFIER LETTER SMALL H) through U+02C1 (MODIFIER LETTER REVERSED GLOTTAL STOP), or U+1D2C (MODIFIER LETTER CAPITAL A) through U+1D61 (MODIFIER LETTER SMALL CHI). These characters are members of the UnicodeCategory.ModifierLetter category.

• Other letters, such as U+05D0 (HEBREW LETTER ALEF) through U+05EA (HEBREW LETTER TAV), U+0621 (ARABIC LETTER HAMZA) through U+063A (ARABIC LETTER GHAIN), or U+4E00 (<CJK Ideograph, First>) through U+9FC3 (<CJK Ideograph, Last>). These characters are members of the UnicodeCategory.OtherLetter category.

IsLetter(Char)

Source:

Char.cs

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

public:
 static bool IsLetter(char c);

public static bool IsLetter (char c);

static member IsLetter : char -> bool

Public Shared Function IsLetter (c As Char) As Boolean

Parameters

c

Char

The Unicode character to evaluate.

Returns

Boolean

true if c is a letter; otherwise, false.

Remarks

This method determines whether a Char is a member of any category of Unicode letter. Unicode letters include the following:

• Uppercase letters, such as U+0041 (LATIN CAPITAL LETTER A) through U+005A (LATIN CAPITAL LETTER Z), or U+0400 (CYRILLIC CAPITAL LETTER IE WITH GRAVE) through U+042F (CYRILLIC CAPITAL LETTER YA). These characters are members of the UnicodeCategory.UppercaseLetter category.

• Lowercase letters, such as U+0061 (LATIN SMALL LETTER A) through U+007A (LATIN SMALL LETTER Z), or U+03AC (GREEK SMALL LETTER ALPHA WITH TONOS) through U+03CE (GREEK SMALL LETTER OMEGA WITH TONOS). These characters are members of the UnicodeCategory.LowercaseLetter category.

• Title case letters, such as U+01C5 (LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON) or U+1FFC (GREEK CAPITAL LETTER OMEGA WITH PROSGEGRAMMENI). These characters are members of the UnicodeCategory.TitlecaseLetter category.

• Modifiers, such as U+02B0 (MODIFIER LETTER SMALL H) through U+02C1 (MODIFIER LETTER REVERSED GLOTTAL STOP), or U+1D2C (MODIFIER LETTER CAPITAL A) through U+1D61 (MODIFIER LETTER SMALL CHI). These characters are members of the UnicodeCategory.ModifierLetter category.

• Other letters, such as U+05D0 (HEBREW LETTER ALEF) through U+05EA (HEBREW LETTER TAV), U+0621 (ARABIC LETTER HAMZA) through U+063A (ARABIC LETTER GHAIN), or U+4E00 (<CJK Ideograph, First>) through U+9FC3 (<CJK Ideograph, Last>). These characters are members of the UnicodeCategory.OtherLetter category.

See also

• IsLetter(Rune)
• Boolean

IsLetter(String, Int32)

Source:

Char.cs

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

public:
 static bool IsLetter(System::String ^ s, int index);

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

static member IsLetter : string * int -> bool

Public Shared Function IsLetter (s As String, index As Integer) As Boolean

Parameters

s

String

A string.

index

Int32

The position of the character to evaluate in s.

Returns

Boolean

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

Exceptions

ArgumentNullException

s is null.

ArgumentOutOfRangeException

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

Remarks

Character positions in a string are indexed starting from zero.

This method determines whether the character at a specified index position in a string is a member of any category of Unicode letter. Unicode letters include the following:

• Uppercase letters, such as U+0041 (LATIN CAPITAL LETTER A) through U+005A (LATIN CAPITAL LETTER Z), or U+0400 (CYRILLIC CAPITAL LETTER IE WITH GRAVE) through U+042F (CYRILLIC CAPITAL LETTER YA). These characters are members of the UnicodeCategory.UppercaseLetter category.

• Lowercase letters, such as U+0061 (LATIN SMALL LETTER A) through U+007A (LATIN SMALL LETTER Z), or U+03AC (GREEK SMALL LETTER ALPHA WITH TONOS) through U+03CE (GREEK SMALL LETTER OMEGA WITH TONOS). These characters are members of the UnicodeCategory.LowercaseLetter category.

• Title case letters, such as U+01C5 (LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON) or U+1FFC (GREEK CAPITAL LETTER OMEGA WITH PROSGEGRAMMENI). These characters are members of the UnicodeCategory.TitlecaseLetter category.

• Modifiers, such as U+02B0 (MODIFIER LETTER SMALL H) through U+02C1 (MODIFIER LETTER REVERSED GLOTTAL STOP), or U+1D2C (MODIFIER LETTER CAPITAL A) through U+1D61 (MODIFIER LETTER SMALL CHI). These characters are members of the UnicodeCategory.ModifierLetter category.

• Other letters, such as U+05D0 (HEBREW LETTER ALEF) through U+05EA (HEBREW LETTER TAV), U+0621 (ARABIC LETTER HAMZA) through U+063A (ARABIC LETTER GHAIN), or U+4E00 (<CJK Ideograph, First>) through U+9FC3 (<CJK Ideograph, Last>). These characters are members of the UnicodeCategory.OtherLetter category.

See also

• Boolean