Prevent duplicate MDI children forms

Question

Is there a way to prevent the opening of a certain form within an MDI container if that said form is already opened?

Answer 1

This code work for me in C#

      private void btn1_Click(object sender, EventArgs e)
            {
               Form2 new_form = new Form2();
                if (new_form.visible)
                    new_form.Show();
                else
                    new_form.ShowDialog();
            }