How to Convert Hex String to Hex Number in C#?

In C#, converting a hexadecimal string to its numeric value is a common operation. Hexadecimal strings represent numbers in base 16 using digits 0-9 and letters A-F. C# provides several methods to convert hex strings to different numeric types depending on your needs.

Syntax

Following is the syntax for converting hex strings using different methods −

Convert.ToInt32(hexString, 16)
Convert.ToSByte(hexString, 16)
int.Parse(hexString, NumberStyles.HexNumber)

Using Convert.ToInt32() Method

The most commonly used method is Convert.ToInt32() which converts a hex string to a 32-bit signed integer −

using System;

public class Program {
   public static void Main() {
      string str = "7D";
      int result = Convert.ToInt32(str, 16);
      Console.WriteLine("Hex string: " + str);
      Console.WriteLine("Decimal value: " + result);
      
      // Converting larger hex values
      string largeHex = "FF";
      Console.WriteLine("Hex " + largeHex + " = " + Convert.ToInt32(largeHex, 16));
   }
}

The output of the above code is −

Hex string: 7D
Decimal value: 125
Hex FF = 255

Using Convert.ToSByte() Method

For smaller hex values that fit in a signed byte (range: -128 to 127), use Convert.ToSByte() −

using System;

public class Program {
   public static void Main() {
      string str = "7D";
      sbyte result = Convert.ToSByte(str, 16);
      Console.WriteLine("Hex string: " + str);
      Console.WriteLine("SByte value: " + result);
      
      // Maximum value for SByte
      string maxHex = "7F";
      Console.WriteLine("Max SByte hex " + maxHex + " = " + Convert.ToSByte(maxHex, 16));
   }
}

The output of the above code is −

Hex string: 7D
SByte value: 125
Max SByte hex 7F = 127

Using int.Parse() with NumberStyles

Another approach is using int.Parse() with NumberStyles.HexNumber −

using System;
using System.Globalization;

public class Program {
   public static void Main() {
      string hexString = "A1B2";
      int result = int.Parse(hexString, NumberStyles.HexNumber);
      Console.WriteLine("Hex string: " + hexString);
      Console.WriteLine("Decimal value: " + result);
      
      // With 0x prefix (remove it first)
      string prefixedHex = "0xDEAD";
      string cleanHex = prefixedHex.Replace("0x", "");
      Console.WriteLine("Original: " + prefixedHex);
      Console.WriteLine("Converted: " + int.Parse(cleanHex, NumberStyles.HexNumber));
   }
}

The output of the above code is −

Hex string: A1B2
Decimal value: 41394
Original: 0xDEAD
Converted: 57005

Comparison of Methods

Conclusion

Converting hex strings to numeric values in C# can be accomplished using Convert.ToInt32(), Convert.ToSByte(), or int.Parse() with NumberStyles.HexNumber. Choose the appropriate method based on the expected range of your hex values and the desired output type.