Generic delegate question

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Barry Gilbert - 23 Oct 2007 16:19 GMT

I have a class that has a generic method that looks something like this:

Public Sub Initialize(Of T As MyBusinessListBase(Of T, C), _
C As MyBusinessBase(Of C)) _
(ByRef dataSource As MyBusinessListBase(Of T, C), _
ByVal reportName As String, ByVal keyProperty As String, _
ByVal callBack As ReportChildCollectionCallback(Of T, C))
' Do stuff to initialize a reportViewer report...
End Sub

Later, this object raises an event. In that event handler, I want to invoke
the callback routine passed into the Initialize method. I'm having trouble
understanding how to store a reference to the callback routine at the class
level so that I can use it in the event handler.

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Jon Skeet [C# MVP] - 23 Oct 2007 18:03 GMT

> I have a class that has a generic method that looks something like this:
>
[quoted text clipped - 10 lines]
> understanding how to store a reference to the callback routine at the class
> level so that I can use it in the event handler.

I don't "do" VB generic declarations, so I can't tell for sure if this
is actually a generic method or just a method within a generic class.
If it's a generic method, you'll have difficulties - you could store
just a Delegate reference and use DynamicInvoke, but it would be better
to make it strongly typed somehow - you may need to introduce an extra
generic type, or parameterize the existing type further.

It's hard to say without knowing more information, I'm afraid.

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Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
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Barry Gilbert - 23 Oct 2007 19:49 GMT

Jon,

Thanks for your reply.

This is a generic method inside a User Control class. I considered making
the class generic, but I found that it's difficult (impossible?) to declare a
user control or form as generic. Am I right about this? I think this would
solve my problem.

Barry

> > I have a class that has a generic method that looks something like this:
> >
[quoted text clipped - 19 lines]
>
> It's hard to say without knowing more information, I'm afraid.

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Jon Skeet [C# MVP] - 23 Oct 2007 20:56 GMT

> Thanks for your reply.
>
> This is a generic method inside a User Control class. I considered making
> the class generic, but I found that it's difficult (impossible?) to declare a
> user control or form as generic. Am I right about this? I think this would
> solve my problem.

I've made a user control generic in the past, but then I've had to
create a specific (non-generic) type derived from it in order to use
it, e.g.

public class WhizzyControl<T> : UserControl
{
... Lots of implementation
}

public class Int32WhizzyControl : WhizzyControl<int>
{
// No code whatsoever
}

That's worked fine for me, although I've only done it once. Would that
help you?

Signature

Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

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Barry Gilbert - 23 Oct 2007 21:27 GMT

Jon,

I've been avoiding taking this on, but I suppose it's time to give it a go.

Thanks for your help.

> > Thanks for your reply.
> >
[quoted text clipped - 19 lines]
> That's worked fine for me, although I've only done it once. Would that
> help you?

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Generic delegate question

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