using System;

using System.Linq;

using System.Text;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        String client_secret = Convert.ToBase64String(Encoding.UTF8.GetBytes("44FEC6A5E3F5454"));

        //{TransactionReference}&{AccountNumber}&{Amount}" HMAC SHA 256 with your secret

        String input = "317724c5-7131-4b83-91d6-fcced195cf04&Chrome&Windows&53687398090908&7839020898";

        //{model.MerchantReference}&{model.BeneficiaryBankCode}&{model.BeneficiaryAccountNumber}&{model.Amount}

        var rs = GenerateHMACSignature(input, client_secret);

        Console.WriteLine(rs);

    }

    public static string GenerateHMACSignature(string input, string secret)

        {

            var secretKeyByteArray = Encoding.UTF8.GetBytes(secret);

            byte[] signature = Encoding.UTF8.GetBytes(input);

​

            using (HMACSHA256 hmac = new HMACSHA256(secretKeyByteArray))

            {

                byte[] signatureBytes = hmac.ComputeHash(signature);

                return Convert.ToBase64String(signatureBytes);

            }

        }

}