CODEWITHSUNDEEP
wpfmvvmwindow
monstr
monstr

Reputation: 1730

Open other window from window

I have some academic question here. I read this question WPF MVVM Get Parent from VIEW MODEL and concluded that ViewModel should not opens any windows itself. So I use Messenger now to send message to ViewModel's Window and Window opens other window - NewWindow. It works fine, but what if NewWindow does something and get some Result has to be passed in MainWindow for further actions? More detailed:

  1. NewWindow opened by button click in Window (OpenNewWindowCommand) and made some calculations.
  2. After calculations NewWindow got some Result (does't matter what exactly is it) and rise a corresponding event - GotSomeResult, where event arg is Result.
  3. This Result has to be passed in MainWindow to further processing, so I bind event handler to GotSomeResult event.

Below you can see all required code to illustrate this scenario.

MainWindow code-behind: 

public MainWindow()
{
    InitializeComponent();
    DataContext = new MainWindowViewModel();

    Messenger.Default.Register<NewWindowMessage>(this, OpenNewWindow);
}

private void OpenNewWindow(NewWindowMessage message)
{
    var newWindow = new NewWindow();
    var newWindowViewModel = (NewWindowViewModel) message.Target;        
    newWindowViewModel.GotSomeResult += ((MetaWindowViewModel)DataContext).ProcessResult;

    newWindow.Owner = this;
    newWindow.DataContext = newWindowViewModel;
    newWindow.ShowDialog();

}

MainWindow ViewModel:

public void OpenNewWindowCommand()
{
    Messenger.Default.Send(new NewWindowMessage(this, new NewWindowViewModel("OpenWindow"), String.Empty));
}

public void ProcessResult(Object someResult)
{
     // Any actions with result
}

newWindowViewModel.GotSomeResult += ((MetaWindowViewModel)DataContext).ProcessResult; --- this string seems problem for me. Is it correct to get access to public method of ViewModel right in theView? Does it violent MVVM pattern?

Upvotes: 1

Views: 109

Answers (1)

franssu
franssu

Reputation: 2430

Why don't you hook the handler to GotSomeResult at the VM level, ie :

public void OpenNewWindowCommand()
{
    var newWindowViewModel = new NewWindowMessage(this, new NewWindowViewModel("OpenWindow"), String.Empty)
    newWindowViewModel.GotSomeResult += this.ProcessResult;

    Messenger.Default.Send();
}

It removes the references to your ViewModel in your codebehind (which indeed should be avoided):

private void OpenNewWindow(NewWindowMessage message)
{
    var newWindow = new NewWindow();

    newWindow.Owner = this;
    newWindow.DataContext = message.Target;
    newWindow.ShowDialog();
}

Upvotes: 2

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