private void btnTK_Click(object sender, EventArgs e)
{
frmTraCuuPhong TK = new frmTraCuuPhong();
TK.ShowDialog();
}
private void TraCuuPhongToolStripMenuItem_Click(object sender, EventArgs e)
{
frmTraCuuPhong child = new frmTraCuuPhong();
child.MdiParent = this;
child.Show();
}