private void but_register_Click(object sender, EventArgs e)
 {
     if (checkInput())
     {
         c1 = label_id.Text;
         c2 = textbox_ncc.Text;
         c3 = funcShare.date(textbox_ngay.Text, textbox_thang.Text, textbox_nam.Text);
         c4 = textbox_nv.Text;
         funcShare.insert("phieu_nhap", "id,ncc_id,ngay_nhap,nhan_vien_id", c1, c2, c3, c4);
         for (int i = 0; i < gridView2.Rows.Count; i++)
         {
             c2 = gridView2.Rows[i].Cells[0].Value.ToString();
             c3 = gridView2.Rows[i].Cells[1].Value.ToString();
             c4 = gridView2.Rows[i].Cells[2].Value.ToString();
             c5 = funcShare.Nvarchar(gridView2.Rows[i].Cells[3].Value.ToString());
             funcShare.insertNoIdentity("chi_tiet_phieu_nhap", "phieu_nhap_id,mat_hang_id,so_luong,don_gia,don_vi", c1, c2, c3, c4, c5);
         }
         LoadPhieuNhap();
         clear();
         funcShare.autoID(label_id, "phieu_nhap");
     }
 }