using System;

using System.Text;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        var key = "";

        var url = "/batch/2022111114";

        var body = @"{

    ""transaction"": 6695646373,

    ""batchID"": 2022111114

}";

        var text = url + body;

        Console.WriteLine(GetHMAC(text, key));

    }

    private static string GetHMAC(string text, string key)

    {

        key = key ?? "";

​

        using (var hmacsha256 = new HMACSHA256(Encoding.UTF8.GetBytes(key)))

        {

            var hash = hmacsha256.ComputeHash(Encoding.UTF8.GetBytes(text));

            return Convert.ToHexString(hash).ToLower();

        }

​

    }

}