Handling "Popup" Window.xaml in PRISM

Question

I'm developing a WPF application with MVVM and PRISM 7.

At some places I'd like to open a new Window.xaml with the click of a button.

So I've created that Window.xaml and am calling it like so when clicking that button/command:

private void OnInstrumentFinderCommand()
{
    var instrumentfinder = new InstrumentFinderWindow();
    var result = instrumentfinder.ShowDialog();
    if (result == true)
    {
        // logic here...   
    }
}

That works fine. The InstrumentFinderWindow opens up and I can interact with it.

But this breaks the loosely coupling which I want to achieve with MVVM.

I know how to use PRISM with View s and Module s, but cannot figure out how I have to handle the Window to achieve the same result as the code above, but loosely coupled resp. not calling it directly from within a ViewModel .

Is there even a way or do I have to handle this completely different?

EDIT: I just want to make clear, that I'm asking about a way to call a System.Windows.Window a MVVM/PRISM-way. Not about a "Yes/No/Cancel" popup dialog.

Answer 1

Calling popup dialog in PRISM-way can be done with Interaction User Experience .

This way is thoroughly described in PRISM documentation and there are bunch of examples how to do it properly in prism samples (25-NotificationRequest, 26-ConfirmationRequest, 27-CustomContent, 28-CustomRequest).

Declare InteractionRequest<T> property in your ViewModel:

public InteractionRequest<Notification> FindInstrumentRequest { get; }

Raise request inside command

private void OnInstrumentFinderCommand() {
    FindInstrumentRequest.Raise(
        new Notification(), 
        notification =>
        {
             //the dialog shown, logic here
        });
}

Add interaction trigger to the window View

<UserControl ...
             xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
             xmlns:prism="http://prismlibrary.com/">

    <i:Interaction.Triggers>
        <prism:InteractionRequestTrigger SourceObject="{Binding FindInstrumentRequest}">
            <prism:PopupWindowAction IsModal="True" CenterOverAssociatedObject="True">
                <prism:PopupWindowAction.WindowContent>
                    <views:InstrumentFinderWindow />
                </prism:PopupWindowAction.WindowContent>
            </prism:PopupWindowAction>
        </prism:InteractionRequestTrigger>
    </i:Interaction.Triggers>

...

</UserControl>

Implement IInteractionRequestAware interface by InstrumentFinderWindowViewModel and finish interaction with FinishInteraction invoking.

public partial class InstrumentFinderWindowViewModel: UserControl, IInteractionRequestAware
{
    private void SelectInstrument()
    {
        FinishInteraction?.Invoke();
    }

    public Action FinishInteraction { get; set; }
    public INotification Notification { get; set; }
}

You can create derived type of NotificationRequest and use it to pass data between window and dialog.

IMPORTANT ADDITION: This interaction mechanism will be removed in feature versions of PRISM. There is new way to handle dialog is being implemented now: DialogService . It is in pre-release version of PRISM library.