using System;

using  System.Security.Cryptography;

using System.Text;

using System.Linq;

public class Program

{

    public static void Main()

    {

​

        string uidTest1Input ="CE5773DD71AC0";

        UInt64 uidTest1 = UInt64.Parse(uidTest1Input, System.Globalization.NumberStyles.HexNumber);

        string conversionBack1 = uidTest1.ToString("X2");

        Console.WriteLine(uidTest1Input + "=>" + uidTest1 + "=>" + conversionBack1);

    }

}