How to tell if an object inherits an interface

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Ron - 11 Mar 2008 19:34 GMT

I have a situation where I need to test if a Control implements from a
specific Interface to avoid an invalid cast exception:

foreach (Control ctrl in this.Controls)
{
// Need to test to see if ctrl inherits interface ICustomControl here
ICustomControl control = (ICustomControl)ctrl;
}

Thanks!
Ron

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Darren - 11 Mar 2008 19:40 GMT

if ( control is ICustomControl )
{
....
}

> I have a situation where I need to test if a Control implements from a
> specific Interface to avoid an invalid cast exception:
[quoted text clipped - 7 lines]
> Thanks!
> Ron

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Ron - 11 Mar 2008 19:57 GMT

Thanks Darren!

> if ( control is ICustomControl )
> {
[quoted text clipped - 12 lines]
>> Thanks!
>> Ron

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Andy - 11 Mar 2008 20:59 GMT

> if ( control is ICustomControl )
> {
[quoted text clipped - 12 lines]
> > Thanks!
> > Ron

Alternately, he can do this:
foreach (Control ctrl in this.Controls)
{
// Need to test to see if ctrl inherits interface ICustomControl here
ICustomControl control = ctrl as ICustomControl;
if ( control != null ) {
// do something
}
}

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Jon Skeet [C# MVP] - 11 Mar 2008 21:02 GMT

> Alternately, he can do this:
> foreach (Control ctrl in this.Controls)
[quoted text clipped - 5 lines]
> }
> }

Or with C# 3 and .NET 3.5:

foreach (ICustomControl ctrl in this.Controls.OfType<ICustomControl>())
{
...
}

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Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
World class .NET training in the UK: http://iterativetraining.co.uk

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How to tell if an object inherits an interface

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