WhenActivated is called twice when used in Views and ViewModels hosted in ViewModelViewHost control

My app uses views, which implement IViewFor<T> interface. The views are registered with the dependency resolver in AppBootstrapper. The app displays the views using ViewModelViewHost control by assigning a corresponding view model to control's ViewModel property. All the view models implement ISupportsActivation interface.

I noticed that WhenActivated is called twice. First it's called when a view and view model get activated. Then on deactivation all disposables are disposed and WhenActivated is called again immediately followed by disposing the disposables.

I am testing with the following code both in view and view model:

this.WhenActivated(disposables => {     Debug.WriteLine("ViewModel activated.");      Disposable         .Create(() =>         {             Debug.WriteLine("ViewModel deactivated.");         })         .AddTo(disposables); }); 

As a result the output looks like this:

// App displays the view:  ViewModel activated. View activated.  // App hides the view:  ViewModel deactivated. View deactivated. ViewModel activated. View activated. ViewModel deactivated. View deactivated. 

The view is hidden by setting ViewModel property of ViewModelViewHost control to null.

Am I doing something wrong?

1 Answers

Answers 1

You can check this link. There is a very good explenation of everything. This is all I can offer without the knowledge of what you did in the "View" itself.

It is possible that the "ViewModel and View" are called twice because you are creating two LoadingViewModels.

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