I have a generic type Store<T>
and use Activator
to make an instance of this type. Now how, after using the Activator, can I cast the resulted object of type object
back to the instantiated type? I know the type that I used to instantiate the generic. Please see the following code:
class Store<T> where T : IStorable
{}
class Beer : IStorable
{}
class BeerStore : Store<Beer>
{}
Type storeType = someObjectThatImplementsIStorable.GetType();
Type classType = typeof(Store<>);
Type[] typeParams = new Type[] { storeType };
Type constructedType = classType.MakeGenericType(typeParams);
object x = Activator.CreateInstance(constructedType, new object[] { someParameter });
What I would like to do is something like this:
var store = (Store<typeof(objectThatImplementsIStorable)>)x;
but that doesn't work for obvious reasons. As an alternative I tried:
var store = (Store<IStorable>)x;
which could possibly work in my opinion, but gives an InvalidCastException
.
How do I get access again to the Store<T>
methods that I know are in the object x
?
Since the actual type T
is available to you only through reflection, you would need to access methods of Store<T>
through reflection as well:
Type constructedType = classType.MakeGenericType(typeParams);
object x = Activator.CreateInstance(constructedType, new object[] { someParameter });
var method = constructedType.GetMethod("MyMethodTakingT");
var res = method.Invoke(x, new object[] {someObjectThatImplementsStorable});
EDIT You could also define an additional IStore
interface that does not use generics, and uses IStorable
instead:
interface IStore {
int CountItems(IStorable item);
}
class Store<T> : IStore where T : IStorable {
int CountItems(IStorable item) {
return count;
}
}
Your Store<T>
would remain generic, but you would get access to its CountItems
by casting to IStore
:
var x = (IStore)Activator.CreateInstance(constructedType, new object[] { someParameter });
var count = x.CountItems((IStorable)someObjectThatImplementsStorable);