After assignment referance object is not null, how is possible?

Question

The object a is null, but I saw the object b was not null in runtime. Why object b is not null in the case?

List<int> a = new List<int>();
List<int> b = a;
a = null;

Answer 1

With this statement a and b 'point' to the same object:

List<int> b = a;

And when you do

a = null;

a 'points' to something different while b is untouched (and still points to the list).

Neither a nor b 'are' the list, they only point, or reference the created object