Delegates: Predicate vs. Action vs. Func

Solution 1:

• 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.

Solution 2:

Action, Func and Predicate all belong to the delegate family.

Action : Action can take n input parameters but it returns void.

Func : Func can take n input parameters but it will always return the result of the provided type. Func<T1,T2,T3,TResult>, here T1,T2,T3 are input parameters and TResult is the output of it.

Predicate : Predicate is also a form of Func but it will always return bool. In simple words it is wrapper of Func<T,bool>.