Points of attention in C # polymorphism

1, the virtual method does not enforce the subclass rewrite, the abstract method must be overridden by the quilt class.

2. As is used to display the conversion class, NULL is returned if the conversion is invalid. Because the display transformation is not known to be able to turn at runtime, the runtime knows that there are no inheritance relationships between the two converters.

is not an inheritance relationship, incompatible. In general, the IS keyword is used to detect compatibility of two classes.

3. Several methods in the super-parent class:

Points of attention in C # polymorphism