Unable to convert IList<MyEntity> to IList<Lightspeed.Entity>

Okaaaay. My actual message disappeared!

Let's try again:

I have a property named 'MyEntityList' defined as Ilist<Entity>.

I have a method on my repository class that returns a generic collection of type IList<MyEntity> where MyEntity is a simple Lightspeed Entity, derived from Entity (or Entity<int> to be more precise, but that doesn't seem to matter here).

When I try to assign the list returned by my method to this property it always fails with an InvalidCastOperation exception (or whatever the thing is called):

Cannot convert from 'System.Collections.Generic.IList<Repository.MyEntity>' to 'System.Collections.Generic.IList<Mindscape.LightSpeed.Entity>'

Why, oh why can I not convert a list of objects derived from Entity to IList<Entity>???

Lucien.

IList isn't covariant (or contravariant come to that).  This is a .NET Framework restriction (scroll down), not anything specific to LightSpeed.  You'll need to create an IList<Entity> and copy the MyEntities into it (or work with an IList<Entity> throughout).

Thanks, Ivan. Not sure whether I get the co- or contravariant bit.:-)

To be more precise I have generic repository method that returns a IList<T> where T : Entity. I want to create or use an equally generic method or property that takes that as a IList<Entity>. So you're saying such a thing is not possible at all? Never realised that!

I have sorted it for now by wrapping my property in a method that takes a IList<T> where T : Entity. In that method I then create a new List<Entity> and add all entities passes into the method to it. That seems to work.

I was hoping for a simpler approach, but no such luck... :-)

Lucien.