Question

I need to use a generic interface like the following:

public interface IContainer<T>
{
    IEnumerable<IContent<T>> Contents { get; }
}

An object implementing this interface is returned by a generic method like the following:

IContainer<T> GetContainer<T>(IProperty property);

Type T is unknown until run-time.

Using reflection I am able to invoke the GetContainer<T> method and get the result.

My problem is that I don’t know how to enumerate the result which has type Object (therefore I cannot cast it to IEnumerable).

I have also tried casting as follows but it does not work (it says “Type is expected”):

var myContainer = genericMethodInfo.Invoke(
                           myService, 
                           new object[] { property })
    as typeof(IContainer<>).MakeGenericType(type);

where type is the runtime type, myService is the service exposing the GetContainer<T> method, and property is of type IProperty as needed.

UPDATE: see my complete solution in my blog: http://stefanoricciardi.com/2010/02/18/generics-with-type-uknown-at-compile-time/

Answer 1

typeof(IContainer<>).MakeGenericType(type) will only evaluate at runtime, while “as” needs to know the type at compiler time.

What I really don’t understand is this comment: My problem is that I don’t know how to enumerate the result which has type Object (therefore I cannot cast it to IEnumerable).

myContainer may be an Object but it can surely be cast to IEnumerable? If it can’t then it can’t be enumerated.