What's so great about Func<> delegate?

delegates lambda expression func
David Browen picture David Browen · Nov 26, 2008 · Viewed 11k times · Source

Sorry if this is basic but I was trying to pick up on .Net 3.5.

Question: Is there anything great about Func<> and it's 5 overloads? From the looks of it, I can still create a similar delgate on my own say, MyFunc<> with the exact 5 overloads and even more.

eg: public delegate TResult MyFunc<TResult>() and a combo of various overloads...

The thought came up as I was trying to understand Func<> delegates and hit upon the following scenario:

Func<int,int> myDelegate = (y) => IsComposite(10);

This implies a delegate with one parameter of type int and a return type of type int. There are five variations (if you look at the overloads through intellisense). So I am guessing that we can have a delegate with no return type?

So am I justified in saying that Func<> is nothing great and just an example in the .Net framework that we can use and if needed, create custom "func<>" delegates to suit our own needs?

Thanks,

Answer

Gishu picture Gishu · Nov 26, 2008

The greatness lies in establishing shared language for better communication.

Instead of defining your own delegate types for the same thing (delegate explosion), use the ones provided by the framework. Anyone reading your code instantly grasps what you are trying to accomplish.. minimizes the time to 'what is this piece of code actually doing?' So as soon as I see a

  • Action = some method that just does something and returns no output
  • Comparison = some method that compares two objects of the same type and returns an int to indicate order
  • Converter = transforms Obj A into equivalent Obj B
  • EventHandler = response/handler to an event raised by some object given some input in the form of an event argument
  • Func = some method that takes some parameters, computes something and returns a result
  • Predicate = evaluate input object against some criteria and return pass/fail status as bool

I don't have to dig deeper than that unless it is my immediate area of concern. So if you feel the delegate you need fits one of these needs, use them before rolling your own.

Disclaimer: Personally I like this move by the language designers.

Counter-argument : Sometimes defining your delegate may help communicate intent better. e.g. System.Threading.ThreadStart over System.Action. So it’s a judgment call in the end.

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