private void btnTao_Click(object sender, EventArgs e)
{
btnTao.Enabled = false;
btnThem.Enabled = true;
string ma = ncc.phatSinhMaTuDong();
cboNCC.Text = ma;
pTemp = new NhaCungCap();
pTemp.MaNhaCungCap = ma;
pTemp.TenNhaCungCap = txtTen.Text;
pTemp.DiaChi = txtDiaChi.Text;
pTemp.SoDienThoai = txtSDT.Text;
txtTen.Text = "";
txtDiaChi.Text = "";
txtSDT.Text = "";
}