using System;

public class Program

{

    public static void Main()

    {

        byte[] bytes = System.Text.Encoding.Unicode.GetBytes("pwd12345Aa!");

        byte[] array = Convert.FromBase64String("rGqX7hy5Zjk5D4mouCgUqw==");

​

        byte[] array2 = new byte[bytes.Length + array.Length];

        Array.Copy(array, array2, array.Length);

        Array.Copy(bytes, 0, array2, array.Length, bytes.Length);

​

        System.Security.Cryptography.HashAlgorithm hashAlgorithm = System.Security.Cryptography.HashAlgorithm.Create("SHA256");

        if (hashAlgorithm is System.Security.Cryptography.KeyedHashAlgorithm)

        {

        (hashAlgorithm as System.Security.Cryptography.KeyedHashAlgorithm).Key = array;

        }

        var resultingCode = Convert.ToBase64String(hashAlgorithm.ComputeHash(array2));

        Console.WriteLine(resultingCode);

    }

}