cost of .net dynamic proxies

Question

What is the cost of using dynamic proxies?

I do not want to clutter my project with Interface Implementations, so I am considering using Dynamic proxies created by some 3rd party library like LinFu , Castle, Unity etc. Do they generate one instance per interface or do I get one for each call.

It is a web app, so whats the performance problem in the long run.

I am also using EF 4.1 (CTP5 at the moment), so if does create proxy classes itself, which makes me wonder if I can use EF's own Dynamic Proxy creating tools.

P.S. yes my interfaces are implemented by concrete classes along with other interfaces and base classes, but sometimes I only need the interface portion of it and not the extra stuff that comes with the concrete class.

All interfaces declare just some part of an EF4.1 POCO. So just getters and setters.

Answer 1

Looks like you need more of a stub rather than a dynamic proxy. Perhaps you might want to take a look at Moq. As far as I know it creates a different instance for every time you create a mock, don't know if internally keeps some sort of a Type cache, though. Mind you, as it's a library targeted for unit tests, so this kind of use would be probably unorthodox.

Answer 2

The opensource Impromptu-Interface, requires c# 4.0, and creates a lightweight proxy type for each Interface and Implementation Type combo you use and keeps them cached.

So creating an interface proxy around a given implementation (an ExpandoObject counts as one type no matter how you set it up) will have a one time cost of generating the proxy type, an Activator.CreateInstance for each time you make a proxy (which isn't bad) and for each call there will be a static invocation which is what you'd have with out the proxy + a dlr dynamic invocation which is very optimized thanks to microsoft.