private void Sign_Click(object sender, RoutedEventArgs e) { var provider = new ProviderUser(); UserModel userModel = provider.Login(userBox.Text, passwordBox.Password); if (userModel == null) { MessageBox.Show("Invalid name or password."); } else { WindowClient windowClient = new WindowClient(provider, new ViewModels.UserViewModel(userModel, provider)); //windowClient.provider = provider; //windowClient.userViewModel = new ViewModels.UserViewModel(userModel, provider); this.IsEnabled = false; windowClient.ShowDialog(); this.IsEnabled = true; } }