内联编辑和更新网格视图数据并将其保存到实体模型数据库的方法

我有这个gridview代码内联编辑和更新数据到实体。我可以编辑内联内容，但不能更新它。我仍然没有得到的问题，为什么它不采取一个文本框包含字符串变量。当我调试它时，它会显示gridview中已经可用的值。

<asp:GridView ID="grdProductInfo" runat="server" 
        AutoGenerateColumns="False" 
         OnRowDeleting="grdProductInfo_RowDeleting" 
         OnRowEditing="grdProductInfo_RowEditing" 
         OnRowCancelingEdit="grdProductInfo_RowCancelingEdit" 
         OnRowDataBound="grdProductInfo_RowDataBound" 
         OnRowUpdating="grdProductInfo_RowUpdating" CellPadding="4" ForeColor="#333333" GridLines="None" DataKeyNames="ProductID" >
        <AlternatingRowStyle BackColor="White" />
        <Columns>
            <asp:TemplateField HeaderText="Product ID">
                <ItemTemplate>
                   <asp:Label ID="lblid" runat="server" Text='<%# Eval("ProductID") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Product Name" ItemStyle-Width="150">
                <ItemTemplate>
                    <asp:Label ID="lblName" runat="server" Text='<%# Eval("ProductName") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="txtName" runat="server" Text='<%# Eval("ProductName") %>'></asp:TextBox>
                </EditItemTemplate>
            <ItemStyle Width="150px"></ItemStyle>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Category ID" ItemStyle-Width="150">
                <ItemTemplate>
                    <asp:Label ID="lblcatId" runat="server" Text='<%# Eval("CategoryID") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="txtcatId" runat="server" Text='<%# Eval("CategoryID") %>'></asp:TextBox>
                </EditItemTemplate>

            </asp:TemplateField>
             <asp:TemplateField HeaderText="Quantity Per Unit" ItemStyle-Width="150">
                <ItemTemplate>
                    <asp:Label ID="lblqpu" runat="server" Text='<%# Eval("QuantityPerUnit") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="txtqpu" runat="server" Text='<%# Eval("QuantityPerUnit") %>'></asp:TextBox>
                </EditItemTemplate>

            </asp:TemplateField>
            <asp:TemplateField HeaderText="Unit Price" ItemStyle-Width="150">
                <ItemTemplate>
                    <asp:Label ID="lblup" runat="server" Text='<%# Eval("UnitPrice") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="txtup" runat="server" Text='<%# Eval("UnitPrice") %>'></asp:TextBox>
                </EditItemTemplate>

            </asp:TemplateField>
            <asp:CommandField ButtonType="Link" ShowEditButton="true" ShowDeleteButton="true" ItemStyle-Width="150">
            </asp:CommandField>
        </Columns>
        <EditRowStyle BackColor="#2461BF" />
        <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
        <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
        <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
        <RowStyle BackColor="#EFF3FB" />
        <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
        <SortedAscendingCellStyle BackColor="#F5F7FB" />
        <SortedAscendingHeaderStyle BackColor="#6D95E1" />
        <SortedDescendingCellStyle BackColor="#E9EBEF" />
        <SortedDescendingHeaderStyle BackColor="#4870BE" />
    </asp:GridView>

cs代码:

protected void grdProductInfo_RowUpdating(object sender,   GridViewUpdateEventArgs e)
    {
         GridViewRow row = grdProductInfo.Rows[e.RowIndex];
         string pname = (row.FindControl("txtName") as TextBox).Text;
         string catId = (row.FindControl("txtcatId") as TextBox).Text;
         string qpu = (row.FindControl("txtqpu") as TextBox).Text;
         string up = (row.FindControl("txtup") as TextBox).Text;

        using (LaunderDBEntities context = new LaunderDBEntities())
            {
                int productID = Convert.ToInt32(grdProductInfo.DataKeys[e.RowIndex].Value);
                Product obj = context.Products.First(x => x.ProductID == productID);
                obj.ProductName = pname;
                obj.CategoryID = Convert.ToInt32(catId);
                obj.QuantityPerUnit = Convert.ToInt32(qpu);
                obj.UnitPrice = Convert.ToInt32(up); 

                context.SaveChanges();
                grdProductInfo.EditIndex = -1;
                this.DataBind();
            }
    }