dotnet remoting: Interface serialization -- dotnet remoting

Interface serialization

Fanette Ozil
8/18/2005 8:57:30 AM

dotnet remoting:

Hello,

Here is the goal of my project :
- to create a simplified API with helper classes for a complex software.
- to protect the software code by redefining a new interface.

My project contains 3 assemblies :
- one that I call "interface dll", which only contains interfaces and
abstract classes. This dll doesn't reference any other assemblies of my
project. It's this dll which is on the client machine. There's no code in it.

- one that I call "server dll" which references the interface dll. All
methods are implemented in it.

- the client part, which only references the interface dll and not the
server dll.

My object model is :

On the dll interface :

public interface IObject
{
int Value
{
get;
set;
}
}

public abstract class Object : MarshalByRefObject, IObject
{
public abstract int Value
{
get;
set;
}
}

public interface IObject1 : IObject
{
...
}

On the server dll :

public abstract class RemoteObject : Object
{
int myValue;

public int Value
{
get { return this.myValue; }
set { this.myValue = value; }
}
}

public class RemoteObject1 : RemoteObject, IObject1
{
...
}

Here is what I do to make my problem appear:

1. The server creates a RemoteObject1 object and sends a reference of type
Object on it to the client. Everything works fine. The client has a reference
of type Object on a RemoteObject1 object. It has access to the methods
defined in IObject.

2. To have access to the methods defined in IObject1, the client can cast
this reference of type Object in a reference of type IObject1, without
problem. The client has now access to the methods defined in IObject1.

3. Then I try to pass a reference of type IObject1 on a RemoteObject1 object
from the client to the server as argument of a function. When doing that the
program does not do anything, neither on server side nor on client side. I do
not enter in the called method on server side. I do not catch any exception
either.

What happened ?

Re: Interface serialization

Fanette Ozil
8/19/2005 8:03:01 AM

I think it was this problem at first.

Then I tried to use only abstract classes without any interfaces. But there
was always the same problem.

In fact, it was a problem with the serialization security. You can find more
details there
http://www.dotnet247.com/247reference/a.aspx?u=http://blogs.msdn.com/sanpil/archive/2004/02/23/78754.aspx

Thank you ...

"Roy Chastain" a Ã©crit :

[quoted text, click to view]

Re: Interface serialization

Roy Chastain
8/19/2005 8:14:06 AM

I believe you are falling into the Interface downcast issue described by Ramor.
Convert your IObject1 to an abstract base class and see if that helps. Of course you will then have multi-inheritance issue.

Page 78 of Ramor's book says (he is talking about shared interfaces)
"...disadvantage to using this process (share interface classes) of sharing the metadata is that you won't be able to pass those
objects as parameters to functions running in a different context (either on the same or another server or on another client)
because the resulting MarshalByRefObject cannot be downcast to these interfaces."

He goes on the explain that the problem goes away if you convert the interfaces to abstract base classes.

I can agree that abstract base classes work. I have about 10 of them in one project right now and they are being passed back and
forth between client and server many times.

HTH.

[quoted text, click to view]
-------------------------------------------
Roy Chastain
KMSYS Worldwide, Inc.

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