Check whether the specified Unicode character is a letter or a decimal digit in C#

To check whether the specified Unicode character is a letter or a decimal digit in C#, use the Char.IsLetterOrDigit() method. This method returns true if the character is a letter (uppercase or lowercase) or a decimal digit (0-9), and false otherwise.

Syntax

Following is the syntax for the Char.IsLetterOrDigit() method −

public static bool IsLetterOrDigit(char c)

Parameters

• c: The Unicode character to evaluate.

Return Value

Returns true if the character is a letter or decimal digit; otherwise, false.

Using IsLetterOrDigit with Decimal Digits

Example

using System;
public class Demo {
   public static void Main() {
      bool res;
      char val = '1';
      Console.WriteLine("Value = " + val);
      res = Char.IsLetterOrDigit(val);
      Console.WriteLine("Is the value a letter or digit? = " + res);
   }
}

The output of the above code is −

Value = 1
Is the value a letter or digit? = True

Using IsLetterOrDigit with Special Characters

Example

using System;
public class Demo {
   public static void Main() {
      bool res;
      char val = '$';
      Console.WriteLine("Value = " + val);
      res = Char.IsLetterOrDigit(val);
      Console.WriteLine("Is the value a letter or digit? = " + res);
   }
}

The output of the above code is −

Value = $
Is the value a letter or digit? = False

Comprehensive Example with Different Character Types

Example

using System;
public class Demo {
   public static void Main() {
      char[] testChars = {'A', 'z', '5', '@', ' ', 'ñ', '²'};
      
      Console.WriteLine("Character\tIsLetterOrDigit");
      Console.WriteLine("-------------------------");
      
      foreach(char ch in testChars) {
         bool result = Char.IsLetterOrDigit(ch);
         Console.WriteLine($"{ch}\t\t{result}");
      }
   }
}

The output of the above code is −

Character	IsLetterOrDigit
-------------------------
A		True
z		True
5		True
@		False
 		False
ñ		True
²		True

Conclusion

The Char.IsLetterOrDigit() method provides a simple way to validate whether a Unicode character is alphanumeric. It returns true for letters (including accented characters) and decimal digits, making it useful for input validation and character classification in C# applications.