C # Concept Memory

New features in C # 4.0 covariant, contravariant

If a class is a direct or indirect base class for another class, it is a weakly typed, direct or indirect subclass that is strongly typed.

Covariance is the assignment of an instance of the Tbar type to a variable of type Tfoo, whereas contravariance is a variable that assigns an instance of the Tfoo type to a tbar type.

Understanding: Covariant is a subclass instance that is copied to an instance of the parent class, and the inverse is the assignment of the parent class instance to the child class instance.

Http://www.cnblogs.com/artech/archive/2011/01/13/variance.html

C # Concept Memory