Down/Up Cast for Control Events?

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lucius - 06 Jun 2007 16:58 GMT

ASP.NET 2.0

I have web controls with their own event handlers that I need to
funnel into a central handler, eg

TypicalEvent( object sender, TypicalEventArgs e )
{
HandleEverything( sender , (EventArgs)e );
}

LinkEvent( object sender, LinkEventArgs e )
{
HandleEverything( sender , (EventArgs)e );
}

SpecialEvent( object sender, SpecialEventArgs e )
{
HandleEverything( sender , (EventArgs)e );
}

And the central event handler is

HandleEverything( object sender , EventArgs e )
{

}

Within "HandleEverything", I would like to know the original Type of
what is in EventArgs and then cast it to the proper Type, because if
it's TypicalEventArgs there is a Value property, if it is
LinkEventArgs there is an AnchorText property, etc.

How can I use Reflection (or Generics?) to "uncast" and use?

Thanks.

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Walter Wang [MSFT] - 07 Jun 2007 06:26 GMT

Hi lucius,

I assume TypicalEventArgs/LinkEventArgs/SpecialEventArgs are all inherited
(directly or indirectly) from EventArgs. You can always use a child type
where a base type is needed without casting. A child type *is* always a
base type.

To cast a reference with base type to a child type, you need to explicitly
cast it, for example:

TypicalEventArgs e2 = (TypicalEventArgs) e;

Of course you need to determine if it's a TypicalEventArgs first:

if (e is TypicalEventArgs) {
TypicalEvent(sender, (TypicalEventArgs) e);
}

Hope this helps.

Sincerely,
Walter Wang (wawang@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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Reply to this Message

Walter Wang [MSFT] - 12 Jun 2007 04:04 GMT

Hi lucius,

If you see this, would you please reply here to let me know if you think
this issue is solved now? Thanks.

Regards,
Walter Wang (wawang@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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Reply to this Message

lucius - 16 Jun 2007 18:58 GMT

Yes, the issue is solved. Thanks.

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Down/Up Cast for Control Events?

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