چرا لقمه رو می پی چونید ؟

       foreach (Form Frm in Application.OpenForms)
{
if (Frm.Text == "Form2")
{
MessageBox.Show("You Cannot Open This form For twice"); return;
}
}
Form2 frm = new Form2();
frm.MdiParent = this;
frm.WindowState = FormWindowState.Maximized;
frm.Show();