C#-WinForm - How to close parent form when child is closed?

Question

This is my issue:

I have 3 forms:

• Form fParent
• Form fChild (is child of fParent)
• Form OpenForm (contains a button A)

I want that When I click button A on fChild, it shows OpenForm , hides fParent and fChild.

How can I do that?

 //code on fChild

OpenForm frm = new OpenForm();

this.Hide();

frm.Show()

Please help me.