Multi-level interfaces -- are they possible?

[Frefaln]

I have a business object with about 10 classes, only one of which is Remoted and available to the web client (a "Controller" class with pass-through stubs to its peer classes). The client accesses the Controller class via an IController interface. It works fine except the interface is only one level deep, which will become more of a problem as the application grows. I'd love to be able to group related method calls into their own category/namespace/interface so that I could call IController like so:

IController.LoanFunctions.GetLoanInfo()
IController.ReportFunctions.GetDailyReport().

I've tried using abstract classes, using nested interfaces (which apparently aren't supported in C#) and everything else I can think of. I haven't found a way to accomplish this while remoting only one object. Any ideas?

[mstraf]

instead of is-a you can use the has-a approach.
Inside the controller class create (private) instances of the other classes, and expose them as public properties.
Will that work for you?
Marco

[Frefaln]

Not sure if this is exactly what you were suggesting, but I ended up splitting Controller into separate classes and having a method return instances of those classes:

public class Controller : MarshalByRefObject,
IController
{
[controller-specific methods]

IXYZInterface GetXYZInterface()
{
return new XYZStubs();
}
}

Then I made a new class containing all the XYZ method stubs:

class XYZStubs : MarshalByRefObject,
IXYZInterface
{
[methods]
}

The only thing I don't like about this approach is that I believe any time a SingleCall SAO (like Controller) returns new instances of a class, the returned classes are treated as CAOs with a default lifetime of 5 minutes. I'd rather not deal with lease management when all I want is a single call for both Controller and the class references returned from it.

[mstraf]

I woudn't create a new class every time:

public class Controller : MarshalByRefObject,
IController
{
[controller-specific methods]
private IXYZInterface m_ixyz; // keep a local instance

IXYZInterface GetXYZInterface()
{
if (m_ixyl == null) m_ixyz = new XYZStubs();
return m_ixyz;
}
}

Marco

[Frefaln]

The Controller class is SingleCall so it really wouldn't matter if I instantiated a new XYZ class every time, the Controller itself only lives for one method call and is then marked for GC.

Still, your suggestion got me thinking and I think this is the way to go for now. I haven't looked into VS.NET 2005 yet to see if it supports nested interfaces (if so, I'll be jumping for joy).