Question

I’m looking at taking a set of objects, let’s say there’s 3 objects alive at the moment, which all implement a common interface, and then wrap those objects inside a fourth object, also implementing the same interface.

The fourth object’s implementations of methods and properties would simply call the relevant bits on those 3 underlying objects. I know that there will be cases here where it won’t make sense to do that, but this is for a service multicast architecture so there’s already a good set of limitations in place.

My question is where to start. The generation of that fourth object should be done in memory, at runtime, so I’m thinking Reflection.Emit, unfortunately I don’t have enough experience with that to even know where to begin.

Do I have to construct an in-memory assembly? It sure looks that way, but I’d just like a quick pointer to where I should start.

Basically I’m looking at taking an interface, and a list of object instances all implementing that interface, and constructing a new object, also implementing that interface, which should “multicast” all method calls and property access to all the underlying objects, at least as much as possible. There will be heaps of problems with exceptions and such but I’ll tackle those bits when I get to them.

This is for a service-oriented architecture, where I would like to have existing code that takes, as an example, a logger-service, to now access multiple logger services, without having to change the code that uses the services. Instead, I’d like to runtime-generate a logger-service-wrapper that internally simply calls the relevant methods on multiple underlying objects.

This is for .NET 3.5 and C#.

Answer 1

(I’m justifying an answer here by adding extra context/info)

Yes, at the moment Reflection.Emit is the only way to solve this.

In .NET 4.0, the Expression class has been extended to support both loops and statement blocks, so for single method usage, a compiled Expression would be a good idea. But even this won’t support multi-method interfaces (just single-method delegates).

Fortunately, I’ve done this previously; see How can I write a generic container class that implements a given interface in C#?