entity framework - GridView binding with custom property in EntityObject derived class fails in ASP.NET -

i've entity framework layer , i've extended class layer. code follows:

public partial class featuremaster : entityobject {     public string parentfeaturename     {                 {             return (from r in global.dc.featuremasters                     r.featureid == featureparentid                     select r).singleordefault().featurename;         }         set         {             featureparentid = (from r in global.dc.featuremasters                                r.featurename == value                                select r).singleordefault().featureid;             reportpropertychanged(("parentfeaturename"));             reportpropertychanged(("featureparentid"));         }     } } 

now wish use same in asp.net page. code asp.net page is:

    <%@ page title="" language="c#" masterpagefile="~/site.master" autoeventwireup="true"     codebehind="listfeaturemaster.aspx.cs" inherits="backend.listfeaturemaster" %> <asp:content id="content1" contentplaceholderid="head" runat="server"> </asp:content> <asp:content id="content2" contentplaceholderid="cpmain" runat="server">     <asp:gridview id="grdrecords" runat="server" allowpaging="true" allowsorting="true"         autogeneratecolumns="false" datakeynames="featureid" datasourceid="entitydatasource1">         <columns>             <asp:commandfield showdeletebutton="true" showeditbutton="true" />             <asp:boundfield datafield="featureid" headertext="featureid" readonly="true" sortexpression="featureid" />             <asp:boundfield datafield="featurename" headertext="featurename" sortexpression="featurename" />             <asp:boundfield datafield="featureparentid" headertext="featureparentid" sortexpression="featureparentid" />             <asp:boundfield datafield="featuredescription" headertext="featuredescription" sortexpression="featuredescription" />             <asp:templatefield headertext="parentfeaturename" sortexpression="parentfeaturename">                 <edititemtemplate>                     <asp:dropdownlist id="dropdownlist1" runat="server" datasourceid="entitydatasource1"                         appenddatabounditems="true" datatextfield="parentfeaturename" datavaluefield="parentfeaturename"                         selectedvalue='<%# bind("parentfeaturename") %>'>                     </asp:dropdownlist>                 </edititemtemplate>                 <itemtemplate>                     <asp:label id="label1" runat="server" text='<%# eval("parentfeaturename") %>'></asp:label>                 </itemtemplate>             </asp:templatefield>         </columns>     </asp:gridview>     <asp:entitydatasource id="entitydatasource1" runat="server" connectionstring="name=backendentities"         defaultcontainername="backendentities" enableflattening="false" entitysetname="featuremasters"         entitytypefilter="featuremaster" enabledelete="true" enableupdate="true">     </asp:entitydatasource>         <asp:entitydatasource id="entitydatasource2" runat="server" connectionstring="name=backendentities"         defaultcontainername="backendentities" enableflattening="false" entitysetname="featuremasters"         entitytypefilter="featuremaster" enabledelete="true" enableupdate="true">     </asp:entitydatasource> </asp:content> 

the trouble when execute code, works on first load , navigation, when try update record, error. please me resolve same.

error message says:

a property named 'parentfeaturename' not found on entity during insert, update, or delete operation. check ensure properties specified binding expressions available data source. 

i think problem don't attach custom property entity, , save it. can have adding customer property entity class

hope helps.