使用MVVM模式在自定义控件或UserControl上调用方法的正确方法？

Question

I'm using PRISM and MVVM in my modular Silverlight application. I'm still trying to figure out PROPER way to do interactions in MVVM fashion and 2 methods that PRISM and samples offer is not something I like for different reasons.

Method 1(PRISM): To use different region adapter. Basically, it involves attached properties on container and injecting view into region. This works almost 100% but negative of this method is that there is no good way to communicate results back. I can use EventAggregator but something doesn't feel right to raise event with data when interaction completed.

Method 2(PRISM): To use InteractionRequest. That involves trigger action and some big boilerplate XAML that I have to repeat on each view.

I'm thinking on creating something on my own which would require creating my own control which will have to be added to each view but with very little XAML and some kind of IPopupService that I can bind this control to. I can pass all needed data via PopupService but in order to actually make action of POPUP happen - I need to call method on this control and that falls apart in MVVM

I wonder how to call method on control in MVVM where view shouldn't be aware of VM ?

Answer 1

View has no option but be aware of VM, since it binds to it.

You could define some kind of a service indeed with a run-time implementation that would interact with the UI and design/test/debug implementation that does something else. You might also publish some events in your VM layer that the View layer would decide how to interpret.

Answer 2

First off, I don't think MVVM is a good choice if you are developing a UserControl that will be consumed by others. A lookless control is what you really should be developing. Jeremiah Morrill has a blog post about this subject.

With that said, you can set the datacontext with XAML if you have a default public constructor.

Inside ControlView.xaml put:

<UserControl.DataContext>
    <local:ControlViewModel />
</UserControl.DataContext>