Creating delegates manually vs using Action/Func delegates

by

The advent of Action and Func family of delegates has rendered custom delegates less used, but the latter still finds uses. Advantages of custom delegates include:

  1. As others have pointed, conveys intent clearly unlike generic Action and Func (Patrik has a very good point about meaningful parameter names).

  2. You can specify ref/out parameters unlike the other two generic delegates. For eg, you can have

    public delegate double ChangeListAction(out string p1, ref int p2);

    but not

    Func<out string, ref int, double> ChangeListAction;

  3. Also, with custom delegates you need to write ChangeListAction (I mean the definition) only once somewhere in your code base, whereas if you don’t define one you will have to litter everywhere Func<string, int, double> all over. Changing the signature will be a hassle in the latter case – a bad case of not being dry.

  4. Can have optional parameters.

    public delegate double ChangeListAction(string p1 = "haha", int p2);

    but not

    Func<string, int, double> ChangeListAction = (p1 = "haha", p2) => (double)p2;

  5. You can have params keyword for parameters of a method, not so with Action/Func.

    public delegate double ChangeListAction(int p1, params string[] p2);

    but not

    Func<int, params string[], double> ChangeListAction;

  6. Well, if you’re truly out of luck and need parameters more than 16 (for the moment) 🙂

As to merits of Action and Func:

  1. It’s quick and dirty, and I use it all over. It makes code short if the use-case is trivial (custom delegates have gone out of fashion with me).

  2. More importantly, its type compatible across domains. Action and Func are framework defined, and they operates seamlessly as long as the parameter types match. You can’t have ChangeSomeAction for ChangeListAction. Linq finds great use of this aspect.

More Related Contents:

  1. Func vs. Action vs. Predicate [duplicate]
  2. Delegates: Predicate vs. Action vs. Func
  3. Uses of Action delegate in C# [closed]
  4. Func delegate with ref variable
  5. Prevent duplicates from array, based on condition [closed]
  6. Why would you use Expression rather than Func?
  7. What are the differences between delegates and events?
  8. converting a .net Func to a .net Expression
  9. Is there a downside to adding an anonymous empty delegate on event declaration?
  10. Get controller and action name from within controller?
  11. Difference Between Invoke and DynamicInvoke
  12. Why must a lambda expression be cast when supplied as a plain Delegate parameter
  13. How do I invoke an extension method using reflection?
  14. Difference between wiring events with and without “new”
  15. Is EndInvoke() optional, sort-of optional, or definitely not optional?
  16. The purpose of delegates [duplicate]
  17. Could we save delegates in a file (C#)
  18. C# Generics won’t allow Delegate Type Constraints
  19. Difference between Delegate.Invoke and Delegate()
  20. When would you use delegates in C#? [closed]
  21. MethodInvoker vs Action for Control.BeginInvoke
  22. Why doesn’t the C# ternary operator work with delegates?
  23. Delegates, Why? [duplicate]
  24. What is Func, how and when is it used
  25. Can’t assign to delegate an anonymous method with less specific parameter type
  26. Explanation of Func
  27. C# – How can I “overload” a delegate?
  28. Can someone distill into proper English what a delegate is?
  29. Is it possible to have a delegate as attribute parameter?
  30. Reflection Performance – Create Delegate (Properties C#)

Leave a Comment