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c#genericsweakeventmanager

WeakEventManager and static event

I am trying to get used to WeakEventManager and I stumble with following:

The only difference between A and B is static, please ignore copy/paste error with nameof ;)

I found this answer regarding generics and static types, but I wonder what WeakEventManager is doing with A then? Somehow it can work with null as source of static event.

I am seeking for a simple answer why static event is ok, but static class as TEventSource suddenly is not.

Code:

public class A
{
    public static event EventHandler Event;
}

public static class B
{
    public static event EventHandler Event;
}

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        WeakEventManager<A, EventArgs>.AddHandler(null, nameof(A.Event), (s, e) => { });
        WeakEventManager<B, EventArgs>.AddHandler(null, nameof(B.Event), (s, e) => { });
    }
}

Error:

Error CS0718
'B': static types cannot be used as type arguments

Solution

  • WeakEventManager can deal with static events, when source is null:

    object sourceKey = (source != null) ? source : StaticSource;

    where StaticSource is a special "event source" for static events.
    This is implementation details of WeakEventManager, and that's why it's OK.

    About static types as generic parameter - this is language limitation. It isn't related specifically to WeakEventManager.