TestConsole/ConsoleApp1/OCPPAuth/Signature.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1.OCPPAuth
{
    internal static class Signature
    {
        public static void Test()
        {
            string signature = GetSignature(
                timestamp: "1731483946",
                partnerid: "523E6CE1-8BA4-4D88-8895-AC05F5B3AE8F",
                saltkey: "L^u9d2Rt@C");
        }

        private static string GetSignature(string timestamp, string partnerid, string saltkey)
        {
            var unencodeText = $"{timestamp}{partnerid}{saltkey}".ToLower();
            var signature = GetSignature(unencodeText);
            return signature;
        }

        private static string GetSignature(string unencodeText)
        {
            if ((unencodeText == null) || (unencodeText.Length == 0))
            {
                return String.Empty;
            }
            unencodeText = unencodeText.ToLower();

            MD5 md5 = MD5.Create();// new MD5CryptoServiceProvider();
            byte[] textToHash = Encoding.UTF8.GetBytes(unencodeText);
            byte[] result = md5.ComputeHash(textToHash);
            return BitConverter.ToString(result).Replace("-", "").ToLower();
        }
    }
}