How to make a simple dynamic proxy in C#

Question

I want to build a dynamic proxy object to add certain functionality to an object.

basically i want to receive an object, wrap it with an object that looks identical to the original i got, and intercept all the calls.

class Wrapper : DynamicProxy// dynamic proxy is not a reall class, but i guess something like this exists... {     public static T Wrap(T obj)     {         return (T) new Wrapper(obj);     }      public override object InterceptCall(MethodInfo info, object[] args)     {         // do stuff     }  } 

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Just to clarify, I want to do something similar to the WCF channel factory...

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I'm adding a bounty, because I need a good way to proxy classes (not interfaces) and to handle non virtual methods (as if I inherited and added a methond under the "new" keyword). I'm sure all this is very possible as the .Net does it.

Answer 1

You could do this with a combination of DynamicObject and ImpromptuInterface but you will have to have an Interface that implements the functions and properties you want to proxy.

public interface IDoStuff {     void Foo(); }  public class Wrapper<T> : DynamicObject {     private readonly T _wrappedObject;      public static T1 Wrap<T1>(T obj) where T1 : class     {         if (!typeof(T1).IsInterface)             throw new ArgumentException("T1 must be an Interface");          return new Wrapper<T>(obj).ActLike<T1>();     }      //you can make the contructor private so you are forced to use the Wrap method.     private Wrapper(T obj)     {         _wrappedObject = obj;     }      public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result)     {         try         {             //do stuff here              //call _wrappedObject object             result = _wrappedObject.GetType().GetMethod(binder.Name).Invoke(_wrappedObject, args);             return true;         }         catch         {             result = null;             return false;         }     } } 

You could of course choose to lose the type-safety and go with a DynamicObject like I showed and then drop the duck-casting.

I made a transparant extendible version of this object proxy, and open-sourced it here.

Answer 2

In addition to Castle.DynamicProxy, there is also LinFu.DynamicProxy on Github.