Converting Between Byte Arrays and Hexadecimal Strings in C#

Introduction

In many applications, particularly those related to cryptography, networking, or data serialization, there is often a need to convert between byte arrays and their hexadecimal string representations. This conversion allows for easier reading, storage, and transmission of binary data by representing it as text.

This tutorial will guide you through the process of converting a byte array to a hexadecimal string and vice versa in C#. We’ll explore both modern methods available in recent .NET versions and traditional approaches that are compatible with older .NET frameworks.

Converting Byte Array to Hexadecimal String

Modern Approach (.NET 5+)

With the introduction of .NET 5, developers can leverage built-in methods for these conversions:

• Convert.ToHexString(byte[]): Converts a byte array into its hexadecimal string representation.

Example:

byte[] byteArray = { 0xDE, 0xAD, 0xBE, 0xEF };
string hexString = Convert.ToHexString(byteArray);
Console.WriteLine(hexString); // Output: DEADBEEF

• Convert.FromHexString(string): Converts a hexadecimal string back into a byte array.

Example:

string hexString = "DEADBEEF";
byte[] byteArray = Convert.FromHexString(hexString);
foreach (var b in byteArray)
{
    Console.Write($"{b:X2} ");
}
// Output: DE AD BE EF

Traditional Approach

For applications running on older .NET frameworks, alternative methods are necessary:

1. Using StringBuilder and Format:

public static string ByteArrayToString(byte[] ba)
{
    StringBuilder hex = new StringBuilder(ba.Length * 2);
    foreach (byte b in ba)
        hex.AppendFormat("{0:x2}", b);
    return hex.ToString();
}

This method constructs the hexadecimal string by formatting each byte to its two-character hexadecimal equivalent.

2. Using BitConverter:

public static string ByteArrayToString(byte[] ba)
{
    return BitConverter.ToString(ba).Replace("-", "");
}

BitConverter.ToString() conveniently formats a byte array into a string with hyphens, which can be removed for a continuous hex representation.

Converting Hexadecimal String to Byte Array

Traditional Approach

For converting a hexadecimal string back to a byte array:

public static byte[] StringToByteArray(string hex)
{
    int numberChars = hex.Length;
    byte[] bytes = new byte[numberChars / 2];
    for (int i = 0; i < numberChars; i += 2)
        bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
    return bytes;
}

This method reads each pair of hexadecimal characters and converts them into a byte using Convert.ToByte().

Considerations for Performance

While the use of Substring in combination with Convert.ToByte is straightforward and easy to understand, it can be inefficient for large datasets due to its memory allocation overhead. For improved performance, alternative methods that avoid these operations should be considered.

Best Practices

• Consistency: Always ensure consistent formatting (e.g., uppercase vs lowercase) when dealing with hex strings.
• Validation: Validate inputs when converting from a hexadecimal string to a byte array to prevent exceptions due to invalid characters or odd-length strings.
• Performance: For high-performance applications, consider implementing more efficient conversion methods that minimize memory allocations.

Conclusion

Understanding how to convert between byte arrays and hexadecimal strings is essential for many programming tasks. With the availability of built-in .NET methods in recent versions, this task has become more straightforward, but traditional approaches remain relevant and useful for legacy systems. By mastering these techniques, you can effectively handle binary data representation and manipulation within your applications.