Show Form

I have Form1 and Form2 and C#.
How can I show the Form2

Form2 myForm;
myForm.ShowDialog(); //spelling might be incorrect..

Form2 myForm = new Form2();
myForm.ShowDialog();

Nobody likes null pointer exceptions.

I have done the following from Form1

Form2 myForm = new Form2();
myForm.Show();

but if I close the initial form that I called this from then the Form2 also is close.

How can I close the calling form, without newly opened form from also closing?

Instead of closing Form1,

Form1.Visible = false;

That still means its in memory and running in the background.

What if a user clicks the X button in the top right, it will still close.

Any better ways to do this.