<asp:TemplateField HeaderText="categoryId" SortExpression="categoryId">
                                    <ItemTemplate><%# Eval("categoryId")%></ItemTemplate>
                                    <EditItemTemplate>
                                        <asp:DropDownList ID="categoryId_dropDownList" runat="server"
                                                          DataSourceID="SqlDataSourceN" DataTextField="Title" 
                                                          DataValueField="Id" SelectedValue='<%#Bind("Id")%>'></asp:DropDownList>
                                    </EditItemTemplate>
                                </asp:TemplateField>