public void send_messages(string sender, string receiver, string message)    //a function to store messages
        {
            messages m = new messages();

            m.set_sender(sender);
            m.set_receiver(receiver);
            m.set_message(message);
            message_list.Add(m);    //adds information to message_list
        }
        public void received_messages(string logged_in) //gets the user who is logged in and displays his received messages
        {
            string rec;

            Console.WriteLine("Message" + "    " + "Sender");
            for (int i = 0; i < message_list.Count; i++)
            {
                messages msg = (messages)message_list[i];
                rec = msg.get_receiver();
                if (rec == logged_in)  //checking if looged in user matches the user from list
                {
                    Console.WriteLine(msg.get_message() + "   " + msg.get_sender());
                }
            }
        }