Challenge 2: A Multicast Action<string> — Possible Solution
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Program.cs:

Action<string> notify = msg => Console.WriteLine("First: " + msg);
notify += msg => Console.WriteLine("Second: " + msg);

notify("Hello!");

Output:

    First: Hello!
    Second: Hello!

Explanation:
The first assignment gives notify a single lambda. The += operator
doesn't replace it -- it ADDS a second lambda to the same delegate,
making notify a genuine multicast delegate referencing two methods.
A single call to notify("Hello!") invokes both, in the order they
were added -- the first-assigned lambda runs first, then the one
added via +=. This is exactly the built-in multicast capability the
chapter names as having no direct Java equivalent.

WHY THIS WORKS AS AN ANSWER
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This demonstrates += genuinely combining two lambdas into one
multicast delegate rather than overwriting the first, with a single
invocation confirming both run in the correct order.