Examples of references to the heap is determined whether the instance of a class
引用.GetType() == Type(class)；
public Type GetType () method is inherited from object.
Base class reference A = new B (); A.GetType () returns be B, rather than A!
Examples of references to the heap is determined whether a specific instance of the class or classes derived from a class
Reference is class
No exception is thrown, it will only return true or false.
The reference into a class instance or it points to a reference base type
Cited as class
No exception is thrown, type conversion failure will return null