An interesting question about C # Polymorphism

The content posted in the rainst Forum is very simple but falls into a trap.

1 class Program
2 {
3 static void main (string [] ARGs)
4 {
5
6 var T = new C ();
7 T. Say ();
8 (T as B). Say ();
9 (T as a). Say ();
10 console. Readline ();
11}
12}
13
14 Class
15 {
16 private int x = 1;
17 Public Virtual void say ()
18 {
19 console. writeline (X. tostring ());
20}
21}
22
23
24 Class B:
25 {
26 private int x = 2;
27 public new void say ()
28 {
29 console. writeline (X. tostring ());
30}
31
32}
33
34 Class C: B
35 {
36}

What is output? Do not compile

Change the T variable declaration to a T = new C ();

What is output now?

Further, change Class B

Class B:
{
Private int x = 2;

Public override void say ()
{
Console. writeline (X. tostring ());
}

}

What about now?