The "pretty" way to make a modal dialog in WPF with Prism and MVVM Pattern

Question

yesterday i used google to find a few ways to make an awesome reusable modal dialog in WPF with PRISM 4.1 and the MVVM pattern. I found some examples but i must say non of those were as "pretty" as i liked them to be.

This one: WPF Modal Dialog (no mvvm -> no use)

This is pretty nice: Showing Dialogs when using the MVVM Pattern (but still it's using a selfmade ServiceLocator which i don't need as i am using the IUnity Container. I could use the logic and rewrite it to Unity but that's not the "pretty" way in my honest opinion.

Well after a while searching the web for informations some blog (can't find the source right now) told me that the PRISM Framework got something called "interaction requests". So i checked out the prism documentation and found a small part under the topic "advanced mvvm scenarios" but the information given in the documentation aren't enough.

I'd like to know if somebody have any good example or any good blogpost about how to realize an awesome modal dialog in prism wpf with mvvm.

EDIT: Regarding the question in the comments:

What makes a modal dialog awesome?

Indeed a good question.

1. It must be modal (while the dialog is open the rest of the UI should be freezed)
2. The dialog view can have it's own viewmodel or at least i would like to give an instance of an object to the dialog view and return an object back to the parent view
3. The view should be an own "xaml" file
4. the dialogresult feature from .NET or at least a way to get a response what the user clicked in the dialog

Answer 1

PRISM 5.0 came up with quick solution to show modal dialogs. Using PopupWindowAction.

<prism:InteractionRequestTrigger SourceObject="{Binding CustomPopupViewRequest, Mode=OneWay}">
    <prism:PopupWindowAction>
        <prism:PopupWindowAction.WindowContent>
            <views:CustomPopupView />
        </prism:PopupWindowAction.WindowContent>
    </prism:PopupWindowAction>
</prism:InteractionRequestTrigger>

Answer 2

Interaction requests require a little more up-front work, but they are definitely the right way to go from the MVVM purist perspective...

I saw an example of how to do this with Prism in Karl Shifflett's MVVM In The Box training extension.

As I remember, the example was pretty rough around the edges, but it should set you in the right direction.

The problem with this kind of in-view "Dialog" is it doesn't allow the dialog to go outside the bounds of the parent window. On the plus side, you can do a lot of fancy layout and animation stuff.