C# RealProxy: generic methods?

Question

I'm trying to handle a call of a generic method through a RealProxy , but I cannot seem to find the information about the actual type of the generic parameter used in the intercepted method call. An excerpt of the code:

    public override IMessage Invoke(IMessage msg)
    {
        ...
        string methodName = (string)msg.Properties["__MethodName"];
        Type[] parameterTypes = (Type[])msg.Properties["__MethodSignature"];
        object[] args = (object[])msg.Properties["__Args"];

        MethodInfo method = typeToProxy.GetMethod(methodName, parameterTypes);
        ...

Let's say I'm proxying an interface like

interface IFactory
{
   TService Create<TService>()
}

When I call the proxy

proxied.Create<MyClass>()

I want to be able to find out the generic parameter is of type MyClass . Is this possible through RealProxy ?

Answer 1

There is an excellent MSDN article about RealProxy which I recommend you read. Among other things, it introduces MethodCallMessageWrapper which saves you the trouble of working directly against the Properties dictionary. From the latter you can get the MethodBase , which in turn contains the generic arguments:

internal class MyProxy : RealProxy
{
   private object m_instance;    
   private MyProxy( object instance ) : base( typeof( IFactory) )
   {
      m_instance = instance;
   }

  public override IMessage Invoke( IMessage message )
  {
     IMethodCallMessage methodMessage =
        new MethodCallMessageWrapper( (IMethodCallMessage) message );

     // Obtain the actual method definition that is being called.
     MethodBase method = methodMessage.MethodBase;

     Type[] genericArgs = method.GetGenericArguments(); //This is what you want

     return new ReturnMessage(...);
  }

  ...
}

Answer 2

For method calls, the IMessage argument should be a IMethodMessage , which has a MethodBase property:

public override IMessage Invoke(IMessage message)
{
    IMethodMessage methodMessage = message as IMethodMessage;
    if (methodMessage != null)
    {
         MethodBase method = methodMessage.MethodBase;
         Type[] genericArgs = method.GetGenericArguments();

         ...
    }
    else
    {
        // not a method call
    }
}