RuntimeBinderException with dynamic in C# 4.0
- by Terence Lewis
I have an interface:
public abstract class Authorizer<T> where T : RequiresAuthorization
{
public AuthorizationStatus Authorize(T record)
{
// Perform authorization specific stuff
// and then hand off to an abstract method to handle T-specific stuff
// that should happen when authorization is successful
}
}
Then, I have a bunch of different classes which all implement RequiresAuthorization, and correspondingly, an Authorizer<T> for each of them (each business object in my domain requires different logic to execute once the record has been authorized).
I'm also using a UnityContainer, in which I register various Authorizer<T>'s. I then have some code as follows to find the right record out of the database and authorize it:
void Authorize(RequiresAuthorization item)
{
var dbItem = ChildContainer.Resolve<IAuthorizationRepository>()
.RetrieveRequiresAuthorizationById(item.Id);
var authorizerType = type.GetType(String.Format("Foo.Authorizer`1[[{0}]], Foo",
dbItem.GetType().AssemblyQualifiedName));
dynamic authorizer = ChildContainer.Resolve(type) as dynamic;
authorizer.Authorize(dbItem);
}
Basically, I'm using the Id on the object to retrieve it out of the database. In the background NHibernate takes care of figuring out what type of RequiresAuthorization it is. I then want to find the right Authorizer for it (I don't know at compile time what implementation of Authorizer<T> I need, so I've got a little bit of reflection to get the fully qualified type). To accomplish this, I use the non-generic overload of UnityContainer's Resolve method to look up the correct authorizer from configuration.
Finally, I want to call Authorize on the authorizer, passing through the object I've gotten back from NHibernate.
Now, for the problem:
In Beta2 of VS2010 the above code works perfectly. On RC and RTM, as soon as I make the Authorize() call, I get a RuntimeBinderException saying "The best overloaded method match for 'Foo.Authorizer<Bar>.Authorize(Bar)' has some invalid arguments". When I inspect the authorizer in the debugger, it's the correct type. When I call GetType().GetMethods() on it, I can see the Authorize method which takes a Bar. If I do GetType() on dbItem it is a Bar.
Because this worked in Beta2 and not in RC, I assumed it was a regression (it seems like it should work) and I delayed sorting it out until after I'd had a chance to test it on the RTM version of C# 4.0. Now I've done that and the problem still persists. Does anybody have any suggestions to make this work?
Thanks
Terence
