C# String to Hex , Hex to Byte Conversion

How can I convert a hex string to a byte array?

Here's a nice fun LINQ example.

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

C# - Convert hex string to byte array of hex values

string hexIpAddress = "0A010248"; // 10.1.2.72 => "0A010248"
byte[] bytes = new byte[hexIpAddress.Length / 2];

for (int i = 0; i < hexIpAddress.Length; i += 2)
    bytes[i/2] = Convert.ToByte(hexIpAddress.Substring(i, 2), 16);

This results in this array:

bytes = {0x0A, 0x01, 0x02, 0x48};

or represented as decimals:

bytes = {10, 1, 2, 72};

or as binaries 00001010, 000000001, 00000010, 01001000 (binary literals are still not supported in C#6).

The values are the same, there is no representation in any base in byte. You can only decide how the values should be represented when converting them to strings again:

foreach(byte b in bytes)
    Console.WriteLine("{0} {0:X}", b);

results in

c# string to hex , hex to byte conversion

You can use the Convert.ToByte(String, Int32) method with the base set to 16 (hexadecimal):

String text = "d7";
byte value = Convert.ToByte(text, 16);

String to byte hex convert

Try Convert.ToByte while providing fromBase (16 in your case)

 // "0A" (string) -> 0x0A == 10 == 0b00001010 (byte)
 byte result = Convert.ToByte(hexString, 16);

 ...

 SomeApiMethod(..., result, ...);

In case you have a Int32 encoded in fact (e.g. "FF120A") and you want to get the last byte:

 // "FF120A" (or "0xFF120A") -> 0xFF120A (int) -> 0x0A (byte)
 // unchecked - we don't want OverflowException on integer overflow
 byte result = unchecked((byte)Convert.ToInt32(hexString, 16));

 ...

 SomeApiMethod(..., result, ...);

Please, notice that the byte (e.g. 0x0A) is always the same, it its string representation that can vary:

 // 00001010 - binary
 Console.WriteLine(Convert.ToString(result, 2).PadLeft(8, '0')); 
 // 10       - decimal
 Console.WriteLine(result);  
 // 0A       - hexadecimal
 Console.WriteLine(result.ToString("X2"));

C# Convert Hex String Array to Byte Array

You have to convert (or parse) string in order to get byte since string and byte are different types:

// 10 == 10d 
byte b = Convert.ToByte("10");     // if "10" is a decimal representation
// 16 == 0x10
byte b = Convert.ToByte("10", 16); // if "10" is a hexadecimal representation

If you want to process an array, you can try a simple Linq:

using System.Linq;

...

string[] hexValues = new string[] {
  "10", "0F", "3E", "42"};

byte[] result = hexValues
  .Select(value => Convert.ToByte(value, 16))
  .ToArray();

If you want to print out result as hexadecimal, use formatting ("X2" format string - at least 2 hexadecimal digits, use captital letters):

// 10, 0F, 3E, 42
Console.Write(string.Join(", ", result.Select(b => b.ToString("X2"))));

Compare with same array but in a different format ("d2" - at least 2 decimal digits)

// 16, 15, 62, 66 
Console.Write(string.Join(", ", result.Select(b => b.ToString("d2"))));

If no format provided, .Net uses default one and represents byte in decimal:

// 16, 15, 62, 66 
Console.Write(string.Join(", ", result));

Hex String To Byte Array C#

I believe you can use Convert.ToByte(), you might have to slice your string in pairs and loop through it.

If you do a quick search there are many topics on this already on stackoverflow

How do you convert Byte Array to Hexadecimal String, and vice versa?

You can also look at this MS example, it is to convert to int, but the idea is the same.
http://msdn.microsoft.com/en-us/library/bb311038.aspx

how to convert hex string values to byte[] in c#

Try Linq: Split and Convert

 string source = "FF AA 1A 23 DF";

 byte[] result = source
   .Split(' ')                               // Split into items 
   .Select(item => Convert.ToByte(item, 16)) // Convert each item into byte
   .ToArray();                               // Materialize as array

Converting String to Hex then into Byte Array

If your final aim is to send byte[], then you can actually skip the middle step and immediately do the conversion from string to byte[] using Encoding.ASCII.GetBytes (provided that you send ASCII char):

string beforeConverting = "HELLO";
byte[] byteData = Encoding.ASCII.GetBytes(beforeConverting); 
//will give you {0x48, 0x45, 0x4C, 0x4C, 0x4F};

If you don't send ASCII, you could find the appropriate Encoding type (like Unicode or UTF32), depends on your need.

That being said, if you still want to convert the hex string to byte array, you could do something something like this:

/// <summary>
/// To convert Hex data string to bytes (i.e. 0x01455687)  given the data type
/// </summary>
/// <param name="hexString"></param>
/// <param name="dataType"></param>
/// <returns></returns>
public static byte[] HexStringToBytes(string hexString) {
  try {
    if (hexString.Length >= 3) //must have minimum of length of 3
      if (hexString[0] == '0' && (hexString[1] == 'x' || hexString[1] == 'X'))
        hexString = hexString.Substring(2);
    int dataSize = (hexString.Length - 1) / 2;
    int expectedStringLength = 2 * dataSize;
    while (hexString.Length < expectedStringLength)
      hexString = "0" + hexString; //zero padding in the front
    int NumberChars = hexString.Length / 2;
    byte[] bytes = new byte[NumberChars];
    using (var sr = new StringReader(hexString)) {
      for (int i = 0; i < NumberChars; i++)
        bytes[i] = Convert.ToByte(new string(new char[2] { (char)sr.Read(), (char)sr.Read() }), 16);
    }
    return bytes;
  } catch {
    return null;
  }
}

And then use it like this:

byte[] byteData = afterConverting.Select(x => HexStringToBytes(x)[0]).ToArray();

The method I put above is more general which can handle input string like 0x05163782 to give byte[4]. For your use, you only need to take the first byte (as the byte[] will always be byte[1]) and thus you have [0] index in the LINQ Select.

The core method used in the custom method above is Convert.ToByte():

bytes[i] = Convert.ToByte(new string(new char[2] { (char)sr.Read(), (char)sr.Read() }), 16);