This print for content only-size & color not accurate 7" X 9-1/4" / casebound / malloy

// If the car is dead, fire Exploded event.

if (carIsDead)

{

if (explodedList != null)

explodedList("Sorry, this car is dead...");

}

else

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8849CH11.qxd  10/1/07  10:43 AM  Page 349

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{

currSpeed += delta;

// Almost dead?

if (10 == maxSpeed - currSpeed

&& almostDeadList != null)

{

almostDeadList("Careful buddy!  Gonna blow!");

}

// Still OK!

if (currSpeed >= maxSpeed)

carIsDead = true;

else

Console.WriteLine("->CurrSpeed = {0}", currSpeed);

}

}

Notice that before we invoke the methods maintained by the almostDeadList and explodedList

member variables, we are checking them against a null value. The reason is that it will be the job of

the caller to allocate these objects by calling the OnAboutToBlow() and OnExploded() helper methods.

If the caller does not call these methods, and we attempt to invoke the delegate’s invocation list,

we will trigger a NullReferenceException and bomb at runtime (which would obviously be a bad

thing!). Now that we have the delegate infrastructure in place, observe the updates to the Program

class:

class Program

{

static void Main(string[] args)

{

Console.WriteLine("***** Delegates as event enablers *****\n");