ILookup and Casting

Question

I got the following objects:

class Base { }
class A : Base {}
class B : Base {}
class C : Base {}

enum BaseType
{
   A,
   B,
   C,
}

ILookup<BaseType, Base> lookup = GetBaseInformation();

The GetBaseInformation method returns me a list of Base objects grouped by base type. With that I would like to set a separated list of properties with each of the BaseTypes and I'm trying to do it like this:

IReadOnlyCollection<A> aTypes = lookup[BaseType.A] as IReadOnlyCollection<A>;
// returns null even if IGrouping<BaseType, A> is there

IReadOnlyCollection<A> aTypes = (IReadOnlyCollection<A>) lookup[BaseType.A];
> Cannot cast 'lookup[BaseType.A]' (which has an actual type 
> of 'System.Linq.Lookup<BaseType,Base>.Grouping') 
> to 'System.Collections.Generic.IReadOnlyCollection<A>'

IReadOnlyCollection<A> aTypes = lookup[BaseType.A].ToList().AsReadOnly()
// returns the list of objects

What am I doing wrong? What is the best way to do this?

I must be missing something. Why would `IGrouping` cast to `IReadOnlyCollection`? It does not, so `as` returns null. Everything works as expected to me — Andrei, Jul 27 '15 at 17:36
I need to cast it to a IReadOnlyCollection property in another object, but how can I do that? This doesn't seem to work either (IReadOnlyCollection ) lookup[BaseType.A].Cast (); — Hélder Gonçalves, Jul 28 '15 at 08:23

ILookup and Casting

0 Answers0