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?

Not an answer to the question, but you shouldn't use an Action for an event. Use either EventHandler or EventHandler as the delegate for events. — Greg Beech, Feb 27 '09 at 01:46
@GregBeech, thanks for the tip, but what is the reason not to use Action here? — I. J. Kennedy, Sep 26 '11 at 18:43
@I.J.Kennedy This answer is pretty awesome http://stackoverflow.com/a/803320/1608072 — caiosm1005, Dec 10 '13 at 02:39

score 39 · Answer 1 · answered Feb 27 '09 at 03:51

39

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();

answered Feb 27 '09 at 03:51

JaredPar

Unless you are passing it to someone elses library, that is using System.Core's Action... – Simon Buchan Feb 27 '09 at 04:29
3

@Simon, in that case you must already be using 3.5 (directly or indirectly) so it's not an issue. – JaredPar Feb 27 '09 at 04:33

score 23 · Accepted Answer · answered Feb 27 '09 at 01:40

23

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.

answered Feb 27 '09 at 01:40

Andrew Hare

Thanks! I did not have a System.Core reference. Even knowing the answer, I still could not find it in the docs. – I. J. Kennedy Feb 27 '09 at 01:49

2 Answers2