it's simple, i just want a explanation about this:
internal class B { // Base class
}
internal class D : B { // Derived class
}
in other class I wrote:
B b3 = new Object(); //compilation time error!
why??? We suposse that all classes inherit from "object"
B is more specialized than Object, therefore you cannot assign an Object instance to a B reference. This is because not every Object is actually a B - only the opposite is true.
Let's assume that you have a field x in the class B. When you instantiate an Object, no memory is reserved for this field, and if you could assign it to a reference of type B, it would therefore try to read or write to unallocated memory, which is not allowed (or useful).