วิธีดึงข้อมูลจากกริดวิว - คือผมติดปัญหานิดนึงตอนกด Remove Row อะครับ

<asp:GridView ID="dgvProductList2" runat="server" AutoGenerateColumns="False" 
     CellPadding="4" ForeColor="#333333" GridLines="None" Visible="False" 
     Width="623px" OnRowDeleting="dgvProductList2_RowDeleting" 
     OnRowEditing="dgvProductList2_RowEditing"
     OnRowCancelingEdit="dgvProductList2_RowCancelingEdit"      
     OnRowUpdating="dgvProductList2_RowUpdating"
     DataKeyNames="ProdBarcode">
     <RowStyle BackColor="#EFF3FB" />
          <Columns>
              <asp:BoundField DataField="ProdBarcode" HeaderText="Barcode" ReadOnly="True">
                    <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" />
                    <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="80px" />
              </asp:BoundField>
             <asp:BoundField DataField="ProdName" HeaderText="Name" ReadOnly="True">
                     <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="150px" />
              </asp:BoundField>
            <asp:BoundField DataField="ProdPrice" HeaderText="Price Per Pack" 
              ReadOnly="True">
                   <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="150px" />
             </asp:BoundField>
             <asp:TemplateField HeaderText="Order Qty">
                   <EditItemTemplate>
                         <asp:TextBox ID="txtQty" runat="server" Width="30px" 
                                 text='<%# Bind("OrderQty") %>'></asp:TextBox>
                   </EditItemTemplate>
                   <ItemTemplate>
                         <asp:Label ID="lblOrderQty" runat="server" Text='<%# Bind("OrderQty") 
                                 %>'></asp:Label>
                   </ItemTemplate>
                   <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
              </asp:TemplateField>
              <asp:BoundField DataField="ShipQty" HeaderText="Shipped Qty" 
                              NullDisplayText="0" ReadOnly="True">
                    <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
              </asp:BoundField>
              <asp:BoundField DataField="TotalPrice" HeaderText="Item Price" ReadOnly="True">
                    <HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" />
                   <ItemStyle HorizontalAlign="Right" VerticalAlign="Middle" Width="50px" />
              </asp:BoundField>
             <asp:TemplateField>
                  <EditItemTemplate>
            <asp:Button ID="btnUpdate" runat="server" CommandName="Update" Text="Update" />
            <asp:Button ID="btnCancel" runat="server" CommandName="Cancel" Text="Cancel" />
                   </EditItemTemplate>
                  <ItemTemplate>
            <asp:Button ID="btnEdit" runat="server" Text=" Edit " CommandName="Edit" />
                   </ItemTemplate>
                   <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" />
             </asp:TemplateField>
             <asp:TemplateField>
                   <ItemTemplate>
          <asp:Button ID="rowToDelete" runat="server" Text="Remove" CommandName="Delete" />
                   </ItemTemplate>
                   <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="50px" />
              </asp:TemplateField>
          </Columns>
          <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
          <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
          <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
         <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
          <EditRowStyle BackColor="#FFFF99" HorizontalAlign="Center" 
                     VerticalAlign="Middle" Width="45px" Wrap="True" />
         <AlternatingRowStyle BackColor="White" />
</asp:GridView>

protected void dgvProductList2_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        getTempProdList();

        string barcode = dgvProductList2.DataKeys[e.RowIndex][0].ToString();
        string cmd = ((Button)dgvProductList2.Rows[e.RowIndex].FindControl("rowToDelete")).ToString();

        DataTable dtProduct = (DataTable)Session["dtProductList"];
        DataRowCollection drc = dtProduct.Rows;
        DataRow delRow = drc.Find(barcode);

        if (delRow != null)
        {
            drc.Remove(delRow);
        }

        Session["dtProductList"] = dtProduct;

        dgvProductList2.DataSource = Session["dtProductList"];
        dgvProductList2.DataBind();

        foreach (GridViewRow r in dgvProductList2.Rows)
        {
            calculatePrice();  //เข้ามาตรงนี้ได้อะครับ
        }
    }
    private void calculatePrice()
    {
        double orderPrice = 0;
        foreach (GridViewRow r in dgvProductList2.Rows)
        {
            double price = double.Parse(r.Cells[2].Text);
            //Label ordQty = (Label)r.FindControl("lblOrderQty");
            //string ORDqty = ordQty.ToString();
            //int orderQty = int.Parse(ORDqty);

            int orderQty = int.Parse(r.Cells[3].Text);  //ติด error ที่บรรทัดนี้อะครับ
            
            double total;
            total = price * orderQty;
            orderPrice += total;

            r.Cells[5].Text = total.ToString("#,##0.00");
        }
        Session["orderPrice"] = orderPrice.ToString("#,##0.00");

        txtOrderPrice.Text = Session["orderPrice"].ToString();
    }