Why does this generic cast fail?

Question

I have the following inheritance:

internal abstract class TeraRow{}

internal class xRow : TeraRow {} // xRow is a child of TeraRow

public IEnumerable

        

Answer 1

You're running afoul of contravariance. You'd need c# 4.0 for that to work. The type IEnumerable can't be exchanged for IEnumerable in 2.0 to 3.5. The msdn article on it is http://blogs.msdn.com/ericlippert/archive/tags/Covariance+and+Contravariance/default.aspx