action delegate with zero parameters

Question

I see this line in many online examples of using the Action delegate:

public event Action MyEvent;

But when I try it in my own code, I get this error

Using the generic type 'System.Action' requires '1' type arguments

The documentation certainly describes a form of Action without any type parameter. What am I missing?

Solution 1

Make sure your application is referencing System.Core.

Edit - also make sure you are targeting .NET 3.5 as the System.Core.dll is part of that version.

Solution 2

Expanding on Andrews answer.

It's perfectly legal to use Action in a non-3.5 scenario. Simply define it yourself.

public delegate void Action();

Comments

[Meydjer Luzzoli]

Not an answer to the question, but you shouldn't use an Action for an event. Use either EventHandler or EventHandler<T> as the delegate for events.

[I. J. Kennedy]

@GregBeech, thanks for the tip, but what is the reason not to use Action here?

[I. J. Kennedy]

Thanks! I did not have a System.Core reference. Even knowing the answer, I still could not find it in the docs.

[AC88]

Unless you are passing it to someone elses library, that is using System.Core's Action...

[JaredPar]

@Simon, in that case you must already be using 3.5 (directly or indirectly) so it's not an issue.