A contravariant delegate can be assigned another delegate of the same type, but with a less derived generic type parameter.
可以向逆变委托分配同一类型的其他委托，但需使用派生程度较小的泛型类型参数。
2
The paper briefly explains the contravariant principle and the effect of the return of afterflow, suggests the method of rendering the return of afterflow.
简要地说明逆变原理及续流回路的作用，提出了绘制续流回路的方法。
3
A type can be declared contravariant in a generic interface or delegate if it is used only as a type of method arguments and not used as a method return type.