newbie question: generic collections cast

[Guest]

I'm passing instance of List<DrawNode> to my method
AddRange(IEnumerable<DrawObject> objects)
But I got this error:

Argument '1': cannot convert from
'System.Collections.Generic.List<MyNamespace.DrawNode>' to
'System.Collections.Generic.IEnumerable<MyNamespace.DrawObject>'

I don't understand why does compiler complain, when List<> has IEnumerable<>
interface and DrawNode is inherited from DrawObject,

so both are just general types. So shouldn't they accept specific inherited
types without explicit cast?

Thank you for answer in advance.

 

[Nicholas Paldino [.NET/C# MVP]]

carry,

No, it should not. The reason is that if you were able to convert the
list to a List<DrawObject> then you could theoretically add DrawObject2
instances to List<DrawNode>, which would end up causing a problem.

Hope this helps.