Introduction:

Hexadecimal, a base-16 numeral system, plays a crucial role in various computing tasks. In C#, converting a hexadecimal string to a byte array is a common operation required for tasks like data transmission and cryptography. This blog will explore different approaches to achieve this conversion, along with detailed explanations and practical examples.

Method 1: Using BitConverter Class

The BitConverter class in C# provides convenient methods to convert data between different primitive types. To convert a hexadecimal string to a byte array using this method, we first need to parse the hexadecimal string into a 32-bit integer and then use BitConverter.GetBytes to convert it to a byte array.

using System;

class HexToByteConverter
{
    static byte[] ConvertHexToByteArray(string hexString)
    {
        int length = hexString.Length;
        byte[] byteArray = new byte[length / 2];

        for (int i = 0; i < length; i += 2)
        {
            byteArray[i / 2] = Convert.ToByte(hexString.Substring(i, 2), 16);
        }

        return byteArray;
    }

    static void Main()
    {
        string hexString = "1A2B3C4D";
        byte[] byteArray = ConvertHexToByteArray(hexString);

        Console.WriteLine("Hexadecimal String: " + hexString);
        Console.WriteLine("Byte Array: " + BitConverter.ToString(byteArray));
    }
}

Output:

Hexadecimal String: 1A2B3C4D
Byte Array: 1A-2B-3C-4D

Method 2: Using LINQ and Enumerable Range

LINQ, a powerful feature in C#, allows for efficient querying and manipulating data. By leveraging LINQ and Enumerable.Range, we can convert each pair of characters in the hexadecimal string to a byte value.

using System;
using System.Linq;

class HexToByteConverter
{
    static byte[] ConvertHexToByteArray(string hexString)
    {
        return Enumerable.Range(0, hexString.Length)
                         .Where(x => x % 2 == 0)
                         .Select(x => Convert.ToByte(hexString.Substring(x, 2), 16))
                         .ToArray();
    }

    static void Main()
    {
        string hexString = "1A2B3C4D";
        byte[] byteArray = ConvertHexToByteArray(hexString);

        Console.WriteLine("Hexadecimal String: " + hexString);
        Console.WriteLine("Byte Array: " + BitConverter.ToString(byteArray));
    }
}

Output:

Hexadecimal String: 1A2B3C4D
Byte Array: 1A-2B-3C-4D

Method 3: Using Bit Manipulation

Another approach to convert a hexadecimal string to a byte array involves bitwise operations. This method is more complex but can be more efficient for large datasets.

using System;

class HexToByteConverter
{
    static byte[] ConvertHexToByteArray(string hexString)
    {
        int length = hexString.Length;
        byte[] byteArray = new byte[length / 2];

        for (int i = 0; i < length; i += 2)
        {
            byteArray[i / 2] = (byte)((GetHexValue(hexString[i]) << 4) | GetHexValue(hexString[i + 1]));
        }

        return byteArray;
    }

    static int GetHexValue(char hexDigit)
    {
        int value = hexDigit - '0';
        return value > 9 ? value - 7 : value;
    }

    static void Main()
    {
        string hexString = "1A2B3C4D";
        byte[] byteArray = ConvertHexToByteArray(hexString);

        Console.WriteLine("Hexadecimal String: " + hexString);
        Console.WriteLine("Byte Array: " + BitConverter.ToString(byteArray));
    }
}

Output:

Hexadecimal String: 1A2B3C4D
Byte Array: 1A-2B-3C-4D

Conclusion:

In this blog, we explored multiple methods for converting a hexadecimal string to a byte array in C#. The first method utilizing BitConverter is simple and easy to understand, but it may not be the most efficient for large datasets. The second method, leveraging LINQ, offers an elegant and concise approach with good performance. The third method based on bit manipulation can be more efficient for significant data volumes, making it a suitable choice for performance-critical applications.