How do I implement IActivationForViewFetcher for a child UserControl?

Question

I've just added ReactiveUI to an existing code base. Of course, for the first control I tried it with I hit a snag. I'm using it with a UserControl embedded in a TabControl. The code looks something like this:

public partial class TabPageControl : UserControl, IViewFor<TestViewModel>
{
    public TabPageControl()
    {
        InitializeComponent();

        ViewModel = new TestViewModel();

        this.WhenActivated(dispose =>
        {
            dispose(this.Bind( ... ));
            dispose(this.BindCommand( ... ));
        });
    }
}

When I run the app, I get the following error message:

Don't know how to detect when TabPageControl is activated/deactivated, you may need to implement IActivationForViewFetcher

So, how do I implement IActivationForViewFetcher? I'm not sure what I'm supposed to do with GetAffinityForView. I'm assuming in GetActivationForView I need to check to see if the UserControl is the currently visible inside the TabControl?

Answer 1

Although I would like to understand how to implement the methods for IActivationForViewFetcher (especially the part where I identify that a control is in the VisualTree) - the real cause of my problem was that my main assembly didn't have the appropriate references (the controls are in a class assembly).

I'm assuming (because I've skimmed the ReactiveUI source) ReactiveUI.Winforms.Registrations needs to be instantiated by the main assembly - which includes registering ActivationForViewFetcher.

Incidentally, the class library is written in C# and the main assembly is VB.NET. So I'm not sure whether this contributed to the problem.

At least it's working now!