Question

I’m not totally convinced this is possible, but here goes. I have a method returning an object, although the actual type is Collection. Now, I can easily cast the object into the collection using

var myCollection = myObject as Collection<MyClassA>;

However the problem I have is that Collection<MyClassA> could alternatively be Collection<MyClassB> or Collection<MyClassC>. All of these MyClassX‘s are inherited from MyBaseClass, so ideally I would like to be able to do something like

var myCollection = myObject as Collection<MyBaseClass>;

However this throws an exception when casting. Is it possible to do this in anyway? I understand that it may be within .Net 4?

Thanks for the help.

EDIT:
OK – The answers so far are very useful, however they only solve the second part of the solution – converting/casting collections.

I am still unsure as to how I should initially cast the object to a collection (without the use of a huge if statement for each of the possible types)

Answer 1

This is only supported with IEnumerable<T> in .NET 4. Check out the difference in the signatures:

IEnumerable<T>:

public interface IEnumerable<out T> : IEnumerable

Collection<T>:

public class Collection<T> : IList<T>, 
ICollection<T>, IEnumerable<T>, IList, ICollection, IEnumerable

That out keyword in the type parameter is what tells .NET to support variance.