public static void RemoveHandler(LongLivedViewModel source, EventHandler handler)
{
_ = source ?? throw new ArgumentNullException(nameof(source));
_ = handler ?? throw new ArgumentNullException(nameof(handler));
CurrentManager.ProtectedRemoveHandler(source, handler);
}
private void ToggleEventHandlingMechanism(object sender, RoutedEventArgs e)
{
_longLivedViewModel = new LongLivedViewModel();
_testWeakEventManager = (EventPattern)((int)(_testWeakEventManager + 1) % 3);
DataContext = _longLivedViewModel;
TestWeakEventManager(_longLivedViewModel);
}
public void ShortLivedViewModel_CustomWeakEventManagerReferenceToLongLivedViewModel_HandlesEventRaisedOnLongLivedViewModel()
{
var longLivedViewModel = new LongLivedViewModel();
var shortLivedViewModel = new ShortLivedViewModel(longLivedViewModel, EventPattern.CustomEventManager);
// act
longLivedViewModel.RaiseEvent();
Assert.AreEqual("ShortLivedViewModel - handled event", longLivedViewModel.Log);
}
ShortLivedViewModel_StrongReferenceToLongLivedViewModel_ShortLivedViewModelUnreferenced_AttemptGarbageCollection_ShortLivedViewModelKeptAliveByStrongReference_HandlesEventRaisedOnLongLivedViewModel()
{
var longLivedViewModel = new LongLivedViewModel();
var shortLivedViewModel = new ShortLivedViewModel(longLivedViewModel, EventPattern.StrongReference);
shortLivedViewModel = null;
GC.Collect();
// act
longLivedViewModel.RaiseEvent();
Assert.AreEqual("ShortLivedViewModel - handled event", longLivedViewModel.Log);
}
ShortLivedViewModel_CustomWeakEventManagerReferenceToLongLivedViewModel_ShortLivedViewModelUnreferenced_AttemptGarbageCollection_ShortLivedViewModelGarbageCollected()
{
var longLivedViewModel = new LongLivedViewModel();
var shortLivedViewModel = new ShortLivedViewModel(longLivedViewModel, EventPattern.CustomEventManager);
var weakReferenceShortLivedViewModel = new WeakReference(shortLivedViewModel);
shortLivedViewModel = null;
// act
GC.Collect();
Assert.IsFalse(weakReferenceShortLivedViewModel.IsAlive);
}
ShortLivedViewModel_StrongReferenceToLongLivedViewModel_ShortLivedViewModelUnreferenced_AttemptGarbageCollection_ShortLivedViewModelKeptAliveByStrongReference()
{
var longLivedViewModel = new LongLivedViewModel();
var shortLivedViewModel = new ShortLivedViewModel(longLivedViewModel, EventPattern.StrongReference);
var weakReferenceShortLivedViewModel = new WeakReference(shortLivedViewModel);
shortLivedViewModel = null;
// act
GC.Collect();
Assert.IsTrue(weakReferenceShortLivedViewModel.IsAlive);
}
ShortLivedViewModel_CustomWeakEventManagerReferenceToLongLivedViewModel_ShortLivedViewModelUnreferenced_AttemptGarbageCollection_ShortLivedViewModelGarbageCollected_DoesNotHandleEventRaisedOnLongLivedViewModel()
{
var longLivedViewModel = new LongLivedViewModel();
var shortLivedViewModel = new ShortLivedViewModel(longLivedViewModel, EventPattern.CustomEventManager);
shortLivedViewModel = null;
GC.Collect();
// act
longLivedViewModel.RaiseEvent();
Assert.IsEmpty(longLivedViewModel.Log);
}
private void TestWeakEventManager(LongLivedViewModel longLivedViewModel)
{
switch (_testWeakEventManager)
{
case EventPattern.StrongReference:
longLivedViewModel.Log = "Using strong reference";
break;
case EventPattern.GenericWeakEventManager:
longLivedViewModel.Log = "Using generic WeakEventManager";
break;
case EventPattern.CustomEventManager:
longLivedViewModel.Log = "Using custom WeakEventManager";
break;
}
var shortLivedViewModel = new ShortLivedViewModel(longLivedViewModel, _testWeakEventManager);
var weakReferenceShortLivedViewModel = new WeakReference(shortLivedViewModel);
longLivedViewModel.Log = "Raise event on LongLivedViewModel";
// expect shortLivedViewModel to handle event
longLivedViewModel.RaiseEvent();
longLivedViewModel.Log = "Clear reference to ShortLivedViewModel";
shortLivedViewModel = null;
longLivedViewModel.Log = "Force garbage collection";
GC.Collect();
longLivedViewModel.Log = $"ShortLivedViewModel.IsAlive = {weakReferenceShortLivedViewModel.IsAlive}";
longLivedViewModel.Log = "Raise event on LongLivedViewModel";
// shortLivedViewModel will only handle the event if not using the WeakEventManager
longLivedViewModel.RaiseEvent();
}