using System;

using System.Security.Cryptography;

using System.Text;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        const string PublicKey = "gTxGf0EVgd2mruMLHOTW";

        const string PrivateKey = "ZyIpcwyP3yibjpQ1CBlW";

        var MerchantTemplateKey = "First-Template"; 

        var msisdn ="" ;

        var operatorCode = "60201";

​

        var productCatalogName = "Courses";

        var productId = "khCourse";

        var language = "2";

        var orderInfo = "4";

        var RedirectUrl = "https://www.google.com";    

​

        var message = MerchantTemplateKey + msisdn + operatorCode + productId + productCatalogName  + language + orderInfo  + RedirectUrl; 

        var theDigest = CalculateDigest(PublicKey, PrivateKey, message);

        Console.WriteLine(theDigest);

    }

​

    public static string CalculateDigest(string publicKey, string privateKey, string message)

    {

        var digest = "";

        var hash = new System.Security.Cryptography.HMACSHA256(System.Text.Encoding.UTF8.GetBytes(privateKey));

        var correctHash = string.Join(string.Empty, hash.ComputeHash(System.Text.Encoding.UTF8.GetBytes(message)).Select(b => b.ToString("x2")));

        digest = publicKey + ":" + correctHash;

​

        return digest;

    }

}