Re: Difference between casting to a class and to an interface

From: Mark Broadbent (no-spam-please_at_no-spam-please.com)
Date: 07/04/04 

Date: Sun, 4 Jul 2004 15:22:19 +0100

that is a very good shout.
I was under the impression that you could only cast an object to an
interface if said object implementated said interface.
After having a play I see (like you) that this is not true.
It seems that the compiler does not type check a cast to an interface
(whether this is by design or not I do not know?)
However in the runtime the cast is succeeding.
Unfortunately the methods exposed by the interface will not succeed if
accessed because of the incompatible object type -so when you try and run
one through the interface ...BANG! exception.

I can see this functionality of being of some benefit in some instances, but
I would love to know whether this is by design.

Nice post, well done! 

-- 
Br,
Mark Broadbent
mcdba , mcse+i
=============
"yufufi" <yufufi@ttnet.net.tr> wrote in message
news:OGtFRlcYEHA.1048@tk2msftngp13.phx.gbl...
> lets say we have a 'shape' class which doesn't implement IComparable
> interface..
>
> compiler doesn't give you error for the lines below..
>
> shape b= new shape();
> IComparable h;
> h=(IComparable)b;
>
> but it complains for the following lines
> shape b= new shape();
> int a;
> a=(int)b;
>
> error is Cannot convert type 'shape' to 'int'
>
> is there difference between casting to a class and casting to an interface
> ?? what does the compiler checks when it is casting to an interface (or
does
> it check anything ?)
>
> Thanx a lot,
>
> yufufi
>
>
>
>
>
>
>
>

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