Whose ToString() would be called?

Question

As we know, int has ToString() method which override the ToString() method of base type Object.

For this following code,

int x = 100;
object y = (object)x;
Console.Write(y.ToString());

(1) Whose ToString() would be called? int or object? WHY?
(2) How we can check/view the truth? By any debug/tool?

Answer 1

Int32.ToString() would be called, because ToString() is called virtually. Int32.ToString() overrides Object.ToString(), so at runtime it effectively replaces Object.ToString().
And at runtime, y is a boxed int.