using System;

using System.Data;

using System.Security.Cryptography;

using System.Text;

using System.Web.Security;

public class Program

{

    public static void Main()

    {

        var password = "DevUser123!#";

        var  passwordKey = "/75hV8kaw0PKpXlC7jcQKA==";

            var bytes1 = Encoding.Unicode.GetBytes(password);

            var key = Convert.FromBase64String(passwordKey);

            var bytes2 = new byte[bytes1.Length + key.Length];

            Array.Copy(key, bytes2, key.Length);

            Array.Copy(bytes1, 0, bytes2, key.Length, bytes1.Length);

            var hashAlgorithm = HashAlgorithm.Create("HMACSHA256");

            Console.WriteLine(Convert.ToBase64String(bytes1));

            Console.WriteLine(Convert.ToBase64String(bytes2));

            if (hashAlgorithm is KeyedHashAlgorithm)

                (hashAlgorithm as KeyedHashAlgorithm).Key = key;

            Console.WriteLine(Convert.ToBase64String(hashAlgorithm.ComputeHash(bytes2)));

    }

}