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Down/Up Cast for Control Events?


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?


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.

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

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