using System;

using System.Security.Cryptography;

​

public class Program

{

    public static void Main()

    {

        string cdrn_domain = "api.testing.cdrn.com";

        string secret_key = "cdrnpassword";

        string api_version = "1.1";

        string method_type = "GET";

        string case_id = "12345";

        string string_date = "2014-06-20T12:06:31Z";

        string string_to_sign = method_type + "\n" + cdrn_domain + "\n" + "/partners/cases/" + case_id + "\n" + "" + "\n" + api_version + "\n" + string_date + "\n";

        var result = CreateSignature(string_to_sign, secret_key);

        Console.WriteLine(result);

    }       

    public static string CreateSignature(string message, string key)

    {

        var encoding = new System.Text.UTF8Encoding();

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

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

        using (var hmacsha1 = new HMACSHA1(keyByte, false))

        {

            byte[] hashmessage = hmacsha1.ComputeHash(messageBytes);

            string hashstring  = BitConverter.ToString(hmacsha1.ComputeHash(messageBytes)).Replace("-","").ToLower();

            return Convert.ToBase64String(encoding.GetBytes(hashstring));

        }

    }           

}