/// <summary>
/// This method is provided to find a <see cref="WeakEventDelegate{TEventArgs}"/>
/// that was added here by passing this <paramref name="weakReference"/>
/// to <see cref="AddHandler"/> --- specifying to use this object as the
/// weak reference to retain this <see cref="EventHandler{TEventArgs}"/>. If
/// an explicit object was passed to the method as the object used to
/// retain the weak reference here, then this returns true if this is the object.
/// Note that if <see langword="null"/> was passed as the weak reference, then
/// this has used the <see cref="EventHandler{TEventArgs}"/>
/// <see cref="Delegate.Target"/> as the weak reference --- and so if that
/// Target is passed to this method, this will return true. Note also
/// that if the weak reference is no longer alive then this returns false.
/// </summary>
/// <param name="weakReference">Not null.</param>
/// <param name="weakEventDelegate">The result if found.</param>
/// <returns>True if this object WAS the object, or
/// <see cref="Delegate.Target"/> passed to <see cref="AddHandler"/> to hold
/// the weak reference here --- and this reference IS still alive.</returns>
public bool TryGetKeyedDelegate(object weakReference, out WeakEventDelegate <TEventArgs> weakEventDelegate)
{
if (weakReference == null)
{
throw new ArgumentNullException(nameof(weakReference));
}
foreach (WeakEventDelegate <TEventArgs> liveDelegate in enumerateLiveDelegates())
{
if (liveDelegate.IsKeyedByWeakReference(weakReference))
{
weakEventDelegate = liveDelegate;
return(true);
}
}
weakEventDelegate = null;
return(false);
}
/// <summary>
/// Adds an event handler. If the <paramref name="weakReference"/>
/// is given, it is used as a weak reference that
/// will release both it and the <paramref name="eventHandler"/>
/// when it becomes released. Otherwise this will test
/// the Target object of the <paramref name="eventHandler"/>,
/// and if not null, uses that. Note that if
/// both are null then the weak reference used IS the <c>eventHandler</c> --- and the
/// code that constructed that must hold a strong reference (the Target is null if the delegate
/// is a static method; and a lambda as an event handler delegate may be immediately
/// collected).
/// </summary>
/// <param name="eventHandler">NOT null. Will be weakly held here.</param>
/// <param name="weakReference">Optional object will determine the weak retention of the
/// <c>eventHandler</c>.</param>
/// <returns>The actual <see cref="WeakEventDelegate{TEventArgs}"/> that has been created
/// and added here.</returns>
/// <exception cref="ArgumentNullException"></exception>
public WeakEventDelegate <TEventArgs> AddHandler(
EventHandler <TEventArgs> eventHandler,
object weakReference = null)
{
if (eventHandler == null)
{
throw new ArgumentNullException(nameof(eventHandler));
}
Purge();
lock (EventDelegates) {
WeakEventDelegate <TEventArgs> weakEventDelegate
= new WeakEventDelegate <TEventArgs>(eventHandler, weakReference);
EventDelegates.Add(weakEventDelegate);
weakEventDelegate.Disposed += handleWeakEventDelegateDisposed;
return(weakEventDelegate);
}
}
