using System;  

using System.Security.Cryptography;  

using System.Text;  

using Newtonsoft.Json; 

public class Program  

{  

    public static string HMACSHA256_Base64(string message, string secret, Encoding encoding)  

    {  

        secret = secret ?? "";  

        byte[] keyByte = encoding.GetBytes(secret);  

        byte[] messageBytes = encoding.GetBytes(message);  

        using (var hmacsha256 = new HMACSHA256(keyByte))  

        {  

            byte[] hashMessage = hmacsha256.ComputeHash(messageBytes);  

            return Convert.ToBase64String(hashMessage);  

        }  

    }  

    public static void Main()  

    {  

        var data = new  

        {  

            user_id = "1175601",  

            merchant_transaction_id = "21787bfdfc04bc8b0cf4b85b1537eb2",  

            status_code = 1000,  

            payment_method = "xl_airtime",  

            amount = "5000",  

            status = "success",  

            currency = "IDR",  

            item_name = "XL1",  

            item_id = "com.huoys.royalcasino.XL1",  

            reference_id = "ff3nugg85643"  

        };  

        string bodyJson = JsonConvert.SerializeObject(data);  

        string secret = "odF60T_HEGGX9xv"; 

        string signature = HMACSHA256_Base64(bodyJson, secret, Encoding.UTF8);  

         Console.WriteLine("json: " + bodyJson);  

        Console.WriteLine("Generated Signature: " + signature);  

    }  

}  

​