Question about Multicast Delegates?

Answer 1

This is not a very well worded question. A multicast delegate is when you have combined separate delegates into one:

delegate int Foo();
Foo a = () => 5;
Foo b = () => 9;
Foo c = a + b; // c is a multicast delegate

When you call c, it invokes a, then b. It returns the return value of the last delegate invoked, so the return value for c is 9.

In my opinion, the answer should be

public delegate void PowerDeviceOn(DateTime d, CancelEventArgs e)

And if one of the methods the delegate is pointing to wants to tell you "false", they should set e.Cancel to true. The delegate can't just return a boolean, because then you'd only get the last delegate's answer.

Answer 2

First of all, by definition, all delegate instances in .NET are multicast delegates, even with 0 or 1 actual functions attached to them.

Strictly speaking, the only delegate (multicast being superfluous) that fits the actual description for problem 1 is D. That is the only functions that accepts a DateTime parameter and returns a bool.

In fact, answer A doesn't meet the requirements explicitly or even conceptually. If the bool parameter were a ref parameter, it would at least be capable of returning a boolean value to the calling code. As it stands, you'd have to check that the return value was > 0.