Confusion about object

Question

class demo

{

int x=10;

public demo()

{

}

static void Main()

{

Console.WriteLine(new demo().x); //1st line

new demo().x = 20; //2nd line

Console.WriteLine(new demo().x);

demo d2=new demo();

d2.x = 30; //3rd line

Console.WriteLine(d2.x);

Console.ReadLine();

}

}

What is the difference between 1st,2nd and 3rd line ??? Why the value is not assigned in 2nd line where as it is assigned in 3rd line ???