Setting presenter property throws 'cannot be used as type parameter' exception

Question

Here's my presenter class:

public class ListPresenter<TViewInterface, TContext> : Presenter<TViewInterface, TContext>
        where TViewInterface : IContextView<TContext>, IListView
        where TContext : IObservableObject
{
     protected override void OnInitializePresentationComplete(dynamic data)
     {
    View.ViewPresenter = (ListPresenter<TViewInterface, TContext>)this;
     }
}

Here's how I am defining the property in the view:

public ListPresenter<IListView, IObservableObject> ViewPresenter { get; set; }

The compile time exception thrown on the ViewPresenter property is "The type IListView cannot be used as type parameter TViewInterface in the generic type or method ListPresenter<TViewInterface, TContect>. There is no implicit reference conversion from IListView to IContextview<IObservableObject>.

Am I defining the ViewPresenter incorrectly? Or am I not casting it correctly? Or both?

score 0 · Answer 1 · answered Jun 20 '13 at 21:13

0

I believe this has to do with your generic where constraints. You're limiting TViewInterface to both IContextView of TContext, and IListView, but this doesn't mean that IListView is an IContextView of TContext, just that whatever type you use is both... Then the error clearly says you're trying to use an IListView as a TViewInterface type, but since it doesn't implement the IContextView interface, it fails.

answered Jun 20 '13 at 21:13

Haney

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I think I understand, thanks. So if what I really want is to access the methods in the list presenter (or, rather from those specific child presenters that inherit from the base list presenter) I need to create an interface to define this specific type of presenter, ie, IListPresenter. – Francine DeGrood Taylor Jun 21 '13 at 16:39
So the top line of my class now reads: public class ListPresenter : Presenter, IListPresenter – Francine DeGrood Taylor Jun 21 '13 at 16:40
And now I can store the interface: View.ViewPresenter = (IListPresenter)this; – Francine DeGrood Taylor Jun 21 '13 at 16:43

Setting presenter property throws 'cannot be used as type parameter' exception

1 Answers1