using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        string MYBytes = "{ 0x4D, 0x5A, 0x90 }";

        string[] hexParts = MYBytes.Split(new char[] { ',', '{', '}' }, StringSplitOptions.RemoveEmptyEntries);

        byte[] bytes = new byte[hexParts.Length];

        for(int i = 0; i < hexParts.Length; i++)

            bytes[i] = Byte.Parse(hexParts[i].Substring(3), NumberStyles.HexNumber);

        foreach(byte b in bytes)

            Console.WriteLine("{0:X2}", b);

    }

}