Window clicked the close button and just hide then click it will show

 this.FormClosing += AFormClosing;


private void AFormClosing(object sender, System.Windows.Forms.FormClosingEventArgs e)
        {
            if (e.CloseReason == CloseReason.UserClosing)
            {
                e.Cancel = true;
                Hide();
            }
        }

 When you want to see the hide form.

newForm.Show();

newForm.Visible=true;