/// <summary>
/// Constructs a new WeakEventHandler
/// </summary>
/// <param name="eventHandler">The Event handler</param>
/// <param name="unregister">Unregister delegate</param>
public WeakEventHandler(EventHandler <E> eventHandler, UnregisterWeakCallback <E> unregister)
{
_TargetRef = new WeakReference(eventHandler.Target);
_OpenHandler = (OpenEventHandler)Delegate.CreateDelegate(typeof(OpenEventHandler),
null, eventHandler.Method);
_Handler = Invoke;
_Unregister = unregister;
}
/// <summary>
/// Invokes the event handler if the source is still alive
/// </summary>
public void Invoke(object sender, E e)
{
T target = (T)_TargetRef.Target;
if (target != null)
{
_OpenHandler.Invoke(target, sender, e);
}
else if (_Unregister != null)
{
_Unregister(_Handler);
_Unregister = null;
}
}
/// <summary>
/// Sxtesion method for EventHandler<E>
/// </summary>
/// <typeparam name="E">The type</typeparam>
/// <param name="eventHandler">The EventHandler</param>
/// <param name="unregister">EventHandler unregister delegate</param>
/// <returns>An EventHandler</returns>
public static EventHandler <E> MakeWeak <E>(this EventHandler <E> eventHandler,
UnregisterWeakCallback <E> unregister) where E : EventArgs
{
if (eventHandler == null)
{
throw new ArgumentNullException("eventHandler");
}
if (eventHandler.Method.IsStatic || eventHandler.Target == null)
{
throw new ArgumentException("Only instance methods are supported.", "eventHandler");
}
Type wehType = typeof(WeakEventHandler <,>).MakeGenericType(eventHandler.Method.DeclaringType, typeof(E));
ConstructorInfo wehConstructor = wehType.GetConstructor(new Type[] {
typeof(EventHandler <E>),
typeof(UnregisterWeakCallback <E>)
});
IWeakEventHandler <E> weh = (IWeakEventHandler <E>)wehConstructor.Invoke(new object[] { eventHandler, unregister });
return(weh.Handler);
}
