private void btnLogout_Click(object sender, EventArgs e)
 {
     frmDangNhap fn = new frmDangNhap();
     fn.Show();
     this.Hide();
 }
 private void buttonX3_Click(object sender, EventArgs e)
 {
     frmDangNhap ft = new frmDangNhap();
     ft.Show();
     this.Hide();
 }