/// <summary>
/// Method invoked when (instead of) a new handler is added to the target event.
/// </summary>
/// <param name="args">Context information.</param>
public override void OnAddHandler(EventInterceptionArgs args)
{
var weakEventClient = args.Handler.Target as IWeakEventClient;
bool supportsWeakReference = weakEventClient != null;
// Throw an exception if the client does not support weak events and we are not allowed to hold strong references.
if (!supportsWeakReference && args.Handler.Target != null && !AllowStrongReferences)
{
throw new InvalidOperationException(
$"Attempt to add a reference to the weak event {args.Event} from type {args.Handler.Target.GetType()}, which does not implement the IWeakEventClient interface.");
}
// Add the handler to our own list.
if (_weakEventHandler.AddHandler(args.Handler, supportsWeakReference))
{
// If it is the first handler we are adding, add a fake handler to ourselves to the target event.
// Whichever handler will add here will be passed to OnInvokeHandler, so it is safe and convenient to pass null.
args.AddHandler(null);
}
// Register the handler to the client to prevent garbage collection of the handler.
if (supportsWeakReference)
{
weakEventClient.RegisterEventHandler(args.Handler);
}
}
/// <summary>
/// Method invoked when (instead of) a new handler is added to the target event.
/// </summary>
/// <param name="args">Context information.</param>
public override void OnAddHandler(EventInterceptionArgs args)
{
// Add the handler to our own list.
if (AddHandler(args.Handler))
{
args.AddHandler(null);
}
// Register the handler to the client to prevent garbage collection of the handler.
DelegateReferenceKeeper.AddReference(args.Handler);
}
/// <summary>
/// Method invoked when (instead of) a new handler is added to the target event.
/// </summary>
/// <param name="args">Context information.</param>
public override void OnAddHandler(EventInterceptionArgs args)
{
// Add the handler to our own list.
if (AddHandler(args.Handler))
{
// If it is the first handler we are adding, add a fake handler to ourselves to the target event.
// Whichever handler will add here will be passed to OnInvokeHandler, so it is safe and convenient to pass null.
args.AddHandler(null);
}
// Register the handler to the client to prevent garbage collection of the handler.
DelegateReferenceKeeper.AddReference(args.Handler);
}
