public void AppropriatelyHandleSubscriptionAndUnsubscription()
{
var sc = new SomeClass();
var handledCount = 0;
var lastCalculationCount = 0;
// call three times before we subscribe
sc.Calculate(Guid.Empty);
sc.Calculate(Guid.Empty);
sc.Calculate(Guid.Empty);
// not subscribed, no updates
Assert.Equal(0, handledCount);
Assert.Equal(0, lastCalculationCount);
// this works, but we can't unsubscribe later since it's anonymous
//sc.CalculateCalled += (o, i) =>
//{
// ++handledCount;
// lastCalculationCount = i;
//};
// generic
void EventRaised(object o, int i)
{
++handledCount;
lastCalculationCount = i;
}
// custom
//void EventRaised(object o, CalculateCalledEventArgs args)
//{
// ++handledCount;
// lastCalculationCount = args.Count;
//}
// that's better
sc.CalculateCalled += EventRaised;
sc.Calculate(Guid.Empty);
sc.Calculate(Guid.Empty);
// subscribed now, values should be updating
Assert.Equal(2, handledCount);
Assert.Equal(5, lastCalculationCount);
// add the handler a second time (2 events per call)
sc.CalculateCalled += EventRaised;
sc.Calculate(Guid.Empty);
sc.Calculate(Guid.Empty);
// double subscribed now, x2 handled per call, last count stays the same
Assert.Equal(6, handledCount);
Assert.Equal(7, lastCalculationCount);
// unsubscribe both
sc.CalculateCalled -= EventRaised;
sc.CalculateCalled -= EventRaised;
sc.Calculate(Guid.Empty);
sc.Calculate(Guid.Empty);
// unsubscribed -> no change
Assert.Equal(6, handledCount);
Assert.Equal(7, lastCalculationCount);
}
