Les Forms problemes

Form test =new Frm2();
test.hide();
this.hide;

Form test =new Frm1();
test.show();
this.close;

Form2 test = new Form2(this);

        private Form1 f1;

        public Form2(Form1 f1)
        {
            InitializeComponent();
            this.f1 = f1;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //ici code pour masquer/afficher le form1
            //avec un test sur f1.Visibility
            if (f1.WindowState == FormWindowState.Normal)
            {
                f1.WindowState = FormWindowState.Minimized;
            }
        }

Form form2 = new Form2();
this.Hide();
form2.ShowModal();
this.Show();