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Note

The 

ArrayList

class is contained within the 

System.Collections

namespace of the 

mscorlib.dll

assembly. Be sure to import this namespace within the file containing your 

Car

definition. Collections (and gener-

ics for that matter) will be examined in detail in Chapter 10.

// This Car and caller can now communicate

// using the IEngineNotification interface.

public class Car

{

// The set of connected sinks.

ArrayList clientSinks = new ArrayList();

// Attach or disconnect from the source of events.

public void Advise(IEngineNotification sink)

{

clientSinks.Add(sink);

}

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305

8849CH09.qxd  10/1/07  10:41 AM  Page 305

---

public void Unadvise(IEngineNotification sink)

{

clientSinks.Remove(sink);

}

...

}

To actually send the events, let’s update the Car.Accelerate() method to iterate over the list of

connections maintained by the ArrayList and fire the correct notification when appropriate. First

of all, add a new Boolean member variable named carIsDead to represent the engine’s state:

class Car

{