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non-standard delegate type with events
f#

data_provider.Stopped.Add(meta_strategy.End)

gives me:

"Stopped has non-standard delegate type and must be accessed using explicit add_Stopped method"

What's up with this?

I found there:
[link:blogs.msdn.com]
[link:tomasp.net]

but they don't really clear the issue up.

FYI, the data_provider instance is coming from some old school C# code and Stopped looks like:

public delegate void StoppedEventHandler();
public event StoppedEventHandler Stopped;

.

In fact, it is not so easy even if i do use add_Stopped. I get:

function has to many args or is used where a function is not expected.

I have to do it like this:

data_provider.add_Stopped(fun _ -> meta_strategy.End())

Seems like it might be nice to have a bit more terseness for wiring up C# events and handlers in F#. I'd guess this must be a common scenario for other people trying to port or build on top of C#.

By on 2/24/2009 7:54 PM ()

Hi Bradford,
when using the "add_EventName" function, you need to create the delegate explicitly, so the following should do the trick:

1
2

 
data_provider.add_OnStuff(new StoppedDelegate(meta_strategy.End))

Handling of events & delegates in F# is a bit difficult, because the idea of delegates is a bit weird for F# - a delegate is almost like a function, so why should it have a different name all the time :-)? E.g. your "StoppedDelegate" looks like a function of type "unit -> unit". Currently, the compiler recognizes standard .NET patterns used when writing delegates & events and translates them into F#-friednly style (in particular, XyzEventHandler taking object and XyzEventArgs), but for non standard delegates & events (which aren't used that often), the compiler just exposes the underlying "add_Xyz" function.

You can of course write some wrappers or extension members to make this a bit nicer for the classes you need to work with.

T.

By on 2/25/2009 4:23 AM ()

I found there is no need to explicitly create the delegate if I eliminated the "StoppedDelegate" and replaced it with the standard "Action." Neverthless, I sill had to explicitly created the "fun _ -> meta_strategy.End()"

By on 2/25/2009 10:34 AM ()

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