C# 4 and .NET 4

204 ❘ ChaPTer 8 deleGAtes, lAmbdAs, And events
}
}
WeakCarInfoEventManager manager =
GetCurrentManager(typeof(WeakCarInfoEventManager))
as WeakCarInfoEventManager;
if (manager == null)
{
manager = new WeakCarInfoEventManager();
SetCurrentManager(typeof(WeakCarInfoEventManager), manager);
}
return manager;
}
}
protected override void StartListening(object source)
{
(source as CarDealer).NewCarInfo += CarDealer_NewCarInfo;
}
void CarDealer_NewCarInfo(object sender, CarInfoEventArgs e)
{
DeliverEvent(sender, e);
}
protected override void StopListening(object source)
{
(source as CarDealer).NewCarInfo = CarDealer_NewCarInfo;
}
code snippet WeakEventsSample/WeakCarInfoEventManager.cs
WPF makes use of the weak event pattern with the event manager classes
CollectionChangedEventManager , CurrentChangedEventManager ,
CurrentChangingEventManager , PropertyChangedEventManager ,
DataChangedEventManager , and LostFocusEventManager .
With the publisher class CarDealer there ’ s no need to change anything. It has the same implementation
as before.
event listener
The listener needs to be changed to implement the interface IWeakEventListener . This interface defi nes
the method ReceiveWeakEvent() that is called from the weak event manager when the event arrives.
In the method implementation the method that should be invoked from the event is invoked, which is
NewCarIsHere() .
using System;
using System.Windows;
namespace Wrox.ProCSharp.Delegates
{
public class Consumer : IWeakEventListener
{
private string name;
public Consumer(string name)
{
this.name = name;
}
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