private void btn_sua_Click(object sender, EventArgs e)
        {
            Form fr_lh = null;

            if (comb_danhmuc.SelectedIndex == 0)
            {
                int       pos = dtgv.CurrentRow.Index;
                int       ID  = Convert.ToInt32(dtgv.Rows[pos].Cells[0].Value);
                LoaiHoang lh  = LoaiHang_BUL.TimLoaiHang(ID);
                fr_lh = new fr_QuanLy_LoaiHang(lh);
            }
            else if (comb_danhmuc.SelectedIndex == 1)
            {
                int     pos = dtgv.CurrentRow.Index;
                int     ID  = Convert.ToInt32(dtgv.Rows[pos].Cells[0].Value);
                HangHoa hh  = HangHoa_BUL.TimLoaiHang(ID);
                fr_lh = new fr_QuanLy_HangHoa(hh);
            }
            else if (comb_danhmuc.SelectedIndex == 2)
            {
                int       pos = dtgv.CurrentRow.Index;
                int       ID  = Convert.ToInt32(dtgv.Rows[pos].Cells[0].Value);
                KhachHang hh  = KhachHang_BUL.TimKhachHang(ID);
                fr_lh = new fr_QuanLy_KhachHang(hh);
            }
            else if (comb_danhmuc.SelectedIndex == 3)
            {
                int        pos = dtgv.CurrentRow.Index;
                int        ID  = Convert.ToInt32(dtgv.Rows[pos].Cells[0].Value);
                NhaCungCap hh  = NhaCungCap_BUL.TimNCC(ID);
                fr_lh = new fr_QuanLy_NhaCungCap(hh);
            }
            else if (comb_danhmuc.SelectedIndex == 4)
            {
                int      pos = dtgv.CurrentRow.Index;
                int      ID  = Convert.ToInt32(dtgv.Rows[pos].Cells[0].Value);
                NhanVien hh  = NhanVien_BUL.TimNhanVien(ID);
                fr_lh = new fr_QuanLy_NhanVien(hh);
            }
            else if (comb_danhmuc.SelectedIndex == 5)
            {
                int            pos = dtgv.CurrentRow.Index;
                int            ID  = Convert.ToInt32(dtgv.Rows[pos].Cells[0].Value);
                DoiTacQuangCao hh  = DoiTacQuangCao_BUL.TimLoaiHang(ID);
                fr_lh = new fr_QuanLy_DoiTacQuanCao(hh);
            }
            if (fr_lh != null)
            {
                fr_lh.FormClosing += Frm2_Closing;
                fr_lh.ShowDialog();
                resetAfterHandle();
            }
        }
        private void btn_them_Click(object sender, EventArgs e)
        {
            Form fr_lh = null;

            if (comb_danhmuc.SelectedIndex == 0)
            {
                fr_lh = new fr_QuanLy_LoaiHang();
            }
            if (comb_danhmuc.SelectedIndex == 1)
            {
                fr_lh = new fr_QuanLy_HangHoa();
            }
            if (comb_danhmuc.SelectedIndex == 2)
            {
                fr_lh = new fr_QuanLy_KhachHang();
            }
            if (comb_danhmuc.SelectedIndex == 3)
            {
                fr_lh = new fr_QuanLy_NhaCungCap();
            }
            if (comb_danhmuc.SelectedIndex == 4)
            {
                fr_lh = new fr_QuanLy_NhanVien();
            }
            if (comb_danhmuc.SelectedIndex == 5)
            {
                fr_lh = new fr_QuanLy_DoiTacQuanCao();
            }


            if (fr_lh != null)
            {
                fr_lh.FormClosing += Frm2_Closing;
                fr_lh.ShowDialog();
                resetAfterHandle();
            }
        }