Gridview update does not trigger / session loss on an update

<asp:GridView ID="Productgv" runat="server" AutoGenerateColumns="false" AutoGenerateEditButton="true" AutoGenerateDeleteButton="true"
            OnRowDeleting="Product_Deleting" OnRowEditing="Product_Editing"
            DataKeyNames="ID" OnRowCancelingEdit="Product_CancelEditing" OnRowUpdating="Product_Updating">
            <Columns>
            <asp:TemplateField HeaderText="ID" Visible="False">
                <ItemTemplate>
                    <asp:HiddenField ID="IDif" runat="server" Value='<%# Eval("ID") %>' />
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:HiddenField ID="IDif" runat="server" Value='<%# Eval("ID") %>' />
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Image alt">
                <ItemTemplate>
                    <asp:Label ID="ImageAlterlbl" runat="server" Text='<%# Eval("ImageAlter") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="ImageAltertb" runat="server" Text='<%# Eval("ImageAlter") %>'></asp:TextBox>
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Image url">
                <ItemTemplate>
                    <img src='<%# Eval("ImageUrl") %>' alt='<%# Eval("ImageAlter") %>' />
                    <asp:HiddenField ID="ImageUrlhf" runat="server" Value='<%# Eval("ImageUrl") %>' />
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:HiddenField ID="ImageUrlhf" runat="server" Value='<%# Eval("ImageUrl") %>' />
                    <table>
                    <tr>
                        <td><asp:Label ID="Changelbl" runat="server" Text="Change picture:"></asp:Label></td>
                        <td><asp:CheckBox ID="Changecb" runat="server" /></td>
                    </tr>
                    <tr>
                        <td colspan="2"><asp:Label ID="Validationlbl" runat="server" Text="" Visible="false" ForeColor="red"></asp:Label></td>
                    </tr>
                    <tr>
                        <td><asp:Label ID="apImageUrllbl" runat="server" Text="Select Image:"></asp:Label></td>
                        <td><asp:FileUpload ID="apImageUrlfu" runat="server" /></td>
                    </tr>
                    <tr>
                        <td><asp:Label ID="Existslbl" runat="server" Text="Overwrite:"></asp:Label></td>
                        <td><asp:CheckBox ID="Existscb" runat="server" /></td>
                    </tr>
                    </table>
                    <img src='<%# Eval("ImageUrl") %>' alt='<%# Eval("ImageAlter") %>' />
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Product Title">
                <ItemTemplate>
                    <asp:Label ID="Titlelbl" runat="server" Text='<%# Eval("Title") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="Titletb" runat="server" Text='<%# Eval("Title") %>'></asp:TextBox>
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Product Info">
                <ItemTemplate>
                    <asp:Label ID="Informationlbl" runat="server" Text='<%# Eval("Information") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="Informationtb" runat="server" Text='<%# Eval("Information") %>'></asp:TextBox>
                </EditItemTemplate>
            </asp:TemplateField>
            </Columns>
            </asp:GridView>     
 
 
 protected void ResourceGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        Label lbl = (Label)ResourceGridview.Rows[e.RowIndex].FindControl("Label1");
        TextBox TextBox1 = (TextBox)ResourceGridview.Rows[e.RowIndex].FindControl("TextBox1");
 
        XmlDocument loResource = new XmlDocument();
        loResource.Load(Server.MapPath("~/App_GlobalResources/" + ResourceListDropdownlist.SelectedItem.ToString()));
 
        XmlNode loRoot = loResource.SelectSingleNode("root/data[@name='" + lbl.Text + "']/value");
 
        if (loRoot != null)
        {
            loRoot.InnerText = TextBox1.Text;
            loResource.Save(Server.MapPath("~/App_GlobalResources/" + ResourceListDropdownlist.SelectedItem.ToString()));
        }
        ResourceGridview.EditIndex = -1;
        ResourceGridviewFill();
    }

                                  

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