Uri.IsHexEncoding() Method in C#

The Uri.IsHexEncoding() method in C# determines whether a character at a specific position in a string is hexadecimal encoded. This method is useful when working with URIs that contain percent-encoded characters, where hexadecimal encoding follows the pattern %XX (a percent sign followed by two hexadecimal digits).

Syntax

Following is the syntax −

public static bool IsHexEncoding(string pattern, int index);

Parameters

• pattern − The string to check for hexadecimal encoding.

• index − The zero-based position in the pattern where the check should begin.

Return Value

Returns true if the character at the specified index is hexadecimal encoded (follows the %XX pattern), otherwise returns false.

Using IsHexEncoding() at Valid Position

This example checks for hexadecimal encoding at index 0, where the pattern starts with % −

using System;

public class Demo {
   public static void Main() {
      string pattern = "%50";
      bool res = Uri.IsHexEncoding(pattern, 0);
      if (res)
         Console.WriteLine("Valid: Hexadecimal Encoded");
      else
         Console.WriteLine("Invalid: Hexadecimal Encoded");
   }
}

The output of the above code is −

Valid: Hexadecimal Encoded

Using IsHexEncoding() at Invalid Position

This example checks for hexadecimal encoding at index 1, which does not start with the % character −

using System;

public class Demo {
   public static void Main() {
      string pattern = "%60";
      bool res = Uri.IsHexEncoding(pattern, 1);
      if (res)
         Console.WriteLine("Valid: Hexadecimal Encoded");
      else
         Console.WriteLine("Invalid: Hexadecimal Encoded");
   }
}

The output of the above code is −

Invalid: Hexadecimal Encoded

Comprehensive Example with Multiple Test Cases

This example demonstrates various scenarios to understand the method behavior better −

using System;

public class Demo {
   public static void Main() {
      string[] patterns = { "%20", "%5A", "%G5", "Hello%20World", "ABC" };
      int[] indices = { 0, 0, 0, 5, 0 };
      
      for (int i = 0; i < patterns.Length; i++) {
         bool result = Uri.IsHexEncoding(patterns[i], indices[i]);
         Console.WriteLine($"Pattern: '{patterns[i]}', Index: {indices[i]}, Result: {result}");
      }
   }
}

The output of the above code is −

Pattern: '%20', Index: 0, Result: True
Pattern: '%5A', Index: 0, Result: True
Pattern: '%G5', Index: 0, Result: False
Pattern: 'Hello%20World', Index: 5, Result: True
Pattern: 'ABC', Index: 0, Result: False

Conclusion

The Uri.IsHexEncoding() method is a utility function that validates whether a specific position in a string contains a valid hexadecimal encoding pattern (%XX). It returns true only when the character at the specified index is % followed by exactly two valid hexadecimal digits.