private void Register_Click(object sender, RoutedEventArgs e)
        {
            // If a file was brought from resources path, fix the absolute path to point to it.
            if (filename.StartsWith("resources"))
            {
                filename = filename.Replace("/", "\\");
                filename = Path.Combine(Environment.CurrentDirectory, filename);
                filename = filename.Replace("bin\\Debug\\", "");
            }
            Image img  = Image.FromFile(filename);
            var   user = CommClient.Register(username.Text, password.Text, email.Text, img);

            if (user != default(SystemUser))
            {
                LoginWindow.user = user;
                Close();
                new MainMenuWindow(loginWindow).Show();
                // Create the invisible system messages window.
                var messagesWindow = new SystemMessageWindow();
                user.Subscribe(messagesWindow);
            }
            else
            {
                errorMessage.Text = "Could not register at the moment.";
            }
        }
        private void Login_Click(object sender, RoutedEventArgs e)
        {
            user = CommClient.Login(username.Text, password.Password);

            if (user == null)
            {
                MessageBox.Show("Wrong input.");
                return;
            }
            Hide();
            errorMessage.Text = "";

            // Create the invisible system messages window.
            var messagesWindow = new SystemMessageWindow();

            user.Subscribe(messagesWindow);
            new MainMenuWindow(this).Show();
        }