Question

Given following classes:

 
class A { int x; } 

class B : A { int y; }

Which code fragments will compile and run successfully?

Cosmo · Accepted Answer

Object a = new A();
Object b = (B)a;

will compile successfully as well, but throw an exception at runtime

Cosmo · Accepted Answer

A a = new B();
a = null;

Cosmo · Accepted Answer

Object a = new B();
B b = a as B;

Cosmo · Answer

B b = new A();

Cosmo · Answer

Object a = new A();
Object b = (B)a;