can't cast ABC to ABC (same class???)

[Ron M. Newman]

Hi,

Under what circumstances can I ever get an exception about not being able to
cast type "ABC" to type "ABC" if there's only one ABC class in the system
and it's loaded from a dynamic assembly?

Thanks
Ron

[Adam Benson]

I have seen this type of behaviour.

For us it occurred under the following circumstances :
When deployed some dll's are not stored in the same directory as the exe.
(We used the config options to set the exe to look in subdirectories for
dll's)
The same dll exists in 2 different folders.

Check to see if your app can find more than one copy of the same dll. Of
course, if all your dlls are in the same folder as your dll what I've said
doesn't apply.

HTH,

Adam.
========
"Ron M. Newman" <co**********@confideltial.comwrote in message
news:e$**************@TK2MSFTNGP04.phx.gbl...

Hi,

Under what circumstances can I ever get an exception about not being able
to cast type "ABC" to type "ABC" if there's only one ABC class in the
system and it's loaded from a dynamic assembly?

Thanks
Ron

[Chris Dunaway]

Ron M. Newman wrote:

Under what circumstances can I ever get an exception about not being able to
cast type "ABC" to type "ABC" if there's only one ABC class in the system
and it's loaded from a dynamic assembly?

You don't have the ABC class code duplicated anywhere do you? That
would cause it.

[Adam Benson]

>if all your dlls are in the same folder as your dll
I meant "if all your dlls are in the same folder as your app exe"

[Gadget]

On Tue, 21 Nov 2006 11:49:27 -0500, Ron M. Newman wrote:

Hi,

Under what circumstances can I ever get an exception about not being able to
cast type "ABC" to type "ABC" if there's only one ABC class in the system
and it's loaded from a dynamic assembly?

Thanks
Ron

If ABC is only in a dynamically loaded class then how are you casting to
it? There can't be a cast unless there is a reference to it, as casting is
a compile time concept, not runtime.
The only cast you can do is to have a third shared DLL with a common
interface 'X', and implement it in your external class, then you can cast
to type 'X' in your main application.
Now assuming you have something like this, which as your code is compiling
I assume you have, then you must make sure the signature used by both main
and external DLLs is the same, and the best way to do this is to put your
interfaces in a separate project and reference it from both other DLLs.

Cheers,
Gadget

[Adam Benson]

If ABC is only in a dynamically loaded class then how are you casting to

it?

The main exe uses a base class, say Base.
Dll1 (no references for this in the main exe build) extends Base to Derived.
Dll2 and Dll3 create \ use Derived and both support an interface known by
the main exe.

The main exe loads up the dlls at run time and, through the interface, calls
Base GiveMeADoodah() in Dll1.
It then calls UseMyDoodah(Base o) in Dll2.

The first thing in Dll2 is :
public UseMyDoodah(Base o)
{
Derived d = (Derived) o;
...
}

And I would guess that line is where his problem his. The solution for us
was to ensure all dlls existed only in one place. When we had this issue
Dll2 and Dll3 were in 2 different sub-dirs (which was fine), but Dll1 had
somehow been deployed into both sub-directories (not fine.) It seemed as
though creation of the object involved using the dll from one sub-directory,
usage of the object involved the dll in a different sub-directory. Even
though it was the same dll you couldn't use an object created by one in the
other. (It helps if you cross your eyes and stand on your head when reading
this.)

Adam.

"Gadget" <ga****@sobell.netwrote in message
news:92*****************************@40tude.net...

On Tue, 21 Nov 2006 11:49:27 -0500, Ron M. Newman wrote:

>Hi,

Under what circumstances can I ever get an exception about not being able
to
cast type "ABC" to type "ABC" if there's only one ABC class in the system
and it's loaded from a dynamic assembly?

Thanks
Ron

If ABC is only in a dynamically loaded class then how are you casting to
it? There can't be a cast unless there is a reference to it, as casting is
a compile time concept, not runtime.
The only cast you can do is to have a third shared DLL with a common
interface 'X', and implement it in your external class, then you can cast
to type 'X' in your main application.
Now assuming you have something like this, which as your code is compiling
I assume you have, then you must make sure the signature used by both main
and external DLLs is the same, and the best way to do this is to put your
interfaces in a separate project and reference it from both other DLLs.

Cheers,
Gadget

[Gadget]

I think I get what you mean :)
I suspect .NET's 'official' solution to this is to ensure your DLL defining
'Base' is registered in the GAC.

Cheers,
Gadget

On Thu, 23 Nov 2006 10:10:58 -0000, Adam Benson wrote:

>If ABC is only in a dynamically loaded class then how are you casting to
it?

The main exe uses a base class, say Base.
Dll1 (no references for this in the main exe build) extends Base to Derived.
Dll2 and Dll3 create \ use Derived and both support an interface known by
the main exe.

The main exe loads up the dlls at run time and, through the interface, calls
Base GiveMeADoodah() in Dll1.
It then calls UseMyDoodah(Base o) in Dll2.

The first thing in Dll2 is :
public UseMyDoodah(Base o)
{
Derived d = (Derived) o;
...
}

And I would guess that line is where his problem his. The solution for us
was to ensure all dlls existed only in one place. When we had this issue
Dll2 and Dll3 were in 2 different sub-dirs (which was fine), but Dll1 had
somehow been deployed into both sub-directories (not fine.) It seemed as
though creation of the object involved using the dll from one sub-directory,
usage of the object involved the dll in a different sub-directory. Even
though it was the same dll you couldn't use an object created by one in the
other. (It helps if you cross your eyes and stand on your head when reading
this.)

Adam.

"Gadget" <ga****@sobell.netwrote in message
news:92*****************************@40tude.net...

>On Tue, 21 Nov 2006 11:49:27 -0500, Ron M. Newman wrote:

>>Hi,

Under what circumstances can I ever get an exception about not being able
to
cast type "ABC" to type "ABC" if there's only one ABC class in the system
and it's loaded from a dynamic assembly?

Thanks
Ron

If ABC is only in a dynamically loaded class then how are you casting to
it? There can't be a cast unless there is a reference to it, as casting is
a compile time concept, not runtime.
The only cast you can do is to have a third shared DLL with a common
interface 'X', and implement it in your external class, then you can cast
to type 'X' in your main application.
Now assuming you have something like this, which as your code is compiling
I assume you have, then you must make sure the signature used by both main
and external DLLs is the same, and the best way to do this is to put your
interfaces in a separate project and reference it from both other DLLs.

Cheers,
Gadget