// Copyright (c) 2008 Daniel Grunwald
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
using System;
using System.Collections.Generic;
namespace WeakEvents
{
/// <summary>
/// A class demonstrating a CommandManager.InvalidateRequery-like event.
/// </summary>
public class WeakReferenceToDelegate
{
List<WeakReference> handlers = new List<WeakReference>();
public event EventHandler Event {
add {
// event is easily made thread-safe is desired
lock (handlers) {
// optionally clean up when adding an event handler to prevent leak
// when event is never fired:
handlers.RemoveAll(wr => !wr.IsAlive);
handlers.Add(new WeakReference(value));
}
}
remove {
lock (handlers) {
handlers.RemoveAll(wr => {
EventHandler target = (EventHandler)wr.Target;
return target == null || target == value;
});
}
}
}
void FireEvent(EventArgs e)
{
EventHandler callHandlers = null;
lock (handlers) {
for (int i = handlers.Count - 1; i >= 0; i--) {
EventHandler target = (EventHandler)handlers[i].Target;
if (target == null)
handlers.RemoveAt(i);
else
callHandlers += target;
}
}
// Call event handlers using a separate event handler list after removing the dead entries
// from the old list to ensure that registering+deregistering events from within an event
// handler works as expected.
if (callHandlers != null)
callHandlers(this, e);
}
}
}