Delegates: Predicate Action Func

Question

Can someone provide a good explanation (hopefully with examples) of these 3 most important delegates:Predicate Action Func.

What other delegates a csharp developer should be aware of?

How often do you use them in production code?

thanks

Answer 1

Actually, I recently ran across this Blog entry which does a pretty good job.

Answer 2

• Predicate: essentially Func<T, bool>; asks the question "does the specified argument satisfy the condition represented by the delegate?" Used in things like List.FindAll.

• Action: Perform an action given the arguments. Very general purpose. Not used much in LINQ as it implies side-effects, basically.

• Func: Used extensively in LINQ, usually to transform the argument, e.g. by projecting a complex structure to one property.

Other important delegates:

• EventHandler/EventHandler<T>: Used all over WinForms

• Comparison<T>: Like IComparer<T> but in delegate form.

Answer 3

In addition to Jon's answer, there is also

• Converter<TInput, TOutput>: It's essentially Func<TInput, TOutput>, but with semantics. Used by List.ConvertAll and Array.ConvertAll, but personally haven't seen it anywhere else.