VISA LOCAL Mode after dispose() via LAN

I am programming an E8257D Signal Generator in Visual Studio 2015 via LAN. My C# code is the following:

class Program
{
          private MessageBasedSession mbSession;
          static void Main(string[] args)
          {
                   MessageBasedSession mbSession = (MessageBasedSession)ResourceManager.GetLocalManager().Open("TCPIP::192.168.100.20::inst0::INSTR"); 
                   mbSession.Write("*IDN?");
                   string temp = mbSession.ReadString();
                   Console.WriteLine(temp);
                   Console.WriteLine("Done1");
                   mbSession.Write("SYST:COMM:GTL\n");
                   Console.WriteLine("Done2");
         

 try
            {
            mbSession.Dispose();
            mbSession = null;
            }
           catch (Exception exp)
           {
           Console.WriteLine(exp.Message);
            }
}

}

After "mbSession.Write("SYST:COMM:GTL\n") instruction; the E8257D goes to LOCAL mode but with the next instruction ”Dispose()”, it comes back again to REMOTE mode. I want the instrument in LOCAL mode when I close the session and it keeps this LOCAL mode after that. Any suggestion. Thanks.