private void metroTile9_Click(object sender, EventArgs e)
 {
     using (FrmThiSinh frm = new FrmThiSinh())
     {
         frm.ShowDialog();
     }
 }
 private void btnMetroInfoAccount_Click(object sender, EventArgs e)
 {
     using (FrmThiSinh frm = new FrmThiSinh())//Open main form and hide login form
     {
         frm.ShowDialog();
     }
 }