Why can't I pass List as a parameter to a method that accepts List<object>?

Question

The following code gives me this error:

Cannot convert from \'System.Collections.Generic.List\' to \'System.Collections.Generic.List\'.

Answer 1

.NET does not have co-variance and contra-variance (yet).

That B derives from A doesn't imply that List derives from List. It doesn't. They are two totally different types.

.NET 4.0 will get limited co-variance and contra-variance.