Convert String to Hex-String in C#

Convert string to hex-string in C#

First you'll need to get it into a byte[], so do this:

byte[] ba = Encoding.Default.GetBytes("sample");

and then you can get the string:

var hexString = BitConverter.ToString(ba);

now, that's going to return a string with dashes (-) in it so you can then simply use this:

hexString = hexString.Replace("-", "");

to get rid of those if you want.

NOTE: you could use a different Encoding if you needed to.

Converting string value to hex decimal

An int contains a number, not a representation of the number. 12000 is equivalent to 0x2ee0:

int a = 12000;
int b = 0x2ee0;
a == b

You can convert from the string "12000" to an int using int.Parse(). You can format an int as hex with int.ToString("X").

C# send hex string as hex

You, probably, are looking for parsing (each string item like "0x5C" should be parsed into corresponding byte: 0x5C):

string Start = "0x5C 0x21 0x5C";

byte[] ByteMessage = Start
  .Split(' ')                               // Split string into items
  .Select(item => Convert.ToByte(item, 16)) // Parse items into corresponding bytes
  .ToArray();                               // Materialize into array

// Back to Hex (let's have a look on what we are going to send): "5C-21-5C"
string HexMessage = string.Join("-", ByteMessage
  .Select(item => item.ToString("X2")));

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"));  

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);

How to Convert Hex String to Hex Number

Convert.ToInt32("3A", 16)

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