private void MainWindow_OnLoaded(object sender, RoutedEventArgs e) { var loginWindow = new LoginDialog(); loginWindow.Owner = this; loginWindow.WindowStartupLocation = WindowStartupLocation.CenterOwner; loginWindow.ShowDialog(); if (loginWindow.LoggedIn) { ButtonSend.IsEnabled = true; client.DataMessageArrived += ClientOnDataMessageArrived; SessionId = loginWindow.SessionId; } }