Question

1) What is the real definition for Action delegate? some definitions describe it is as polymorphic conditional map , some say it *Applied decision Table *.

(You may ask what will you achieve by knowing definition , if i know it i can understand its real purpose).

2) Thanks Binary Worrier,Andrew Hare of stackoverflow for giving nice examples.
When i declare

string[] words = "This is as easy as it looks".Split(' ');
 `Array.ForEach(words, p => Console.WriteLine(p));`

i can understand what it actually does.But when i declare ,How does C# interpret when i
declare

     Dictionary<SomeEnum, Action<User>> methodList =
     new Dictionary<SomeEnum, Action<User>>()
     methodList.Add(SomeEnum.One, DoSomething);
     methodList.Add(SomeEnum.Two, DoSomethingElse);

Does it store collections of Actions in dictionary ?.unfortunately as the example was incomplete i did not get it.

3) What is the functional difference between Action , Function ,Predicate delagets?

Answer 1

It’s just another delegate. Action<T> is declared like this:

void Action<T>(T item)

It’s just “something which acts on a single item”. There are generic overloads with more type parameters and normal parameters. In itself, an Action<T> isn’t an applied decision table or anything like that – it’s just a delegate which can do “something” with an item.

The dictionary example is just a dictionary with enum values as keys, and actions as values – so you can look up what to do based on the enum value, and then pass in a User reference for it to act on.

As for Func vs Action vs Predicate: Func is like Action, but returning a value. Predicate is similar, but always returns bool, and there aren’t the range of generic overloads, just Predicate<T> to determine if an item “matches” the predicate.