Binding navigation property to RadGrid while using EntityDataSource control - telerik

Question

I'm new to Entity Framework and I got stuck in an issue while trying to bind a navigation property (foreign key reference) to a dropdownlist. I have Telerik RadGrid control which gets the data using a EntityDataSource control. Here is the model description:
Applications: AppId, AppName, ServerId
Servers: ServerId, ServerName
The Applicaitons.ServerId is a foreign key reference to Servers.ServerId. The RadGrid lists the applications and allows the user to insert/update/delete an application. I want to show the server names as a dropdownlist in edit mode which I'm not able to. . Here is my aspx code:
<telerik:RadGrid ID="gridApplications" runat="server" Skin="Sunset"
AllowAutomaticInserts="True" AllowAutomaticDeletes="True"
AllowPaging="True" AllowAutomaticUpdates="True"
AutoGenerateColumns="False" OnItemCreated="gridApplications_ItemCreated"
DataSourceID="applicationsEntityDataSource" Width="50%"
OnItemInserted="gridApplications_ItemInserted"
OnItemUpdated="gridApplications_ItemUpdated"
OnItemDeleted="gridApplications_ItemDeleted" GridLines="None">
<MasterTableView CommandItemDisplay="Top" AutoGenerateColumns="False" DataKeyNames="AppId" DataSourceID="applicationsEntityDataSource">
<RowIndicatorColumn>
<HeaderStyle Width="20px" />
</RowIndicatorColumn>
<ExpandCollapseColumn>
<HeaderStyle Width="20px" />
</ExpandCollapseColumn>
<Columns>
<telerik:GridEditCommandColumn ButtonType="ImageButton" UniqueName="EditCommandColumn" HeaderText="Edit" ItemStyle-Width="10%">
</telerik:GridEditCommandColumn>
<telerik:GridButtonColumn CommandName="Delete" Text="Delete" UniqueName="DeleteColumn" ConfirmText="Are you sure you want to delete this application?" ConfirmTitle="Confirm Delete" ConfirmDialogType="Classic" ItemStyle-Width="10%" HeaderText="Delete">
</telerik:GridButtonColumn>
<telerik:GridBoundColumn DataField="AppId" UniqueName="AppId" Visible="false" HeaderText="Application Id" ReadOnly="true">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="AppName" UniqueName="AppName" HeaderText="Application Name" MaxLength="30" ItemStyle-Width="40%">
</telerik:GridBoundColumn>
<telerik:GridTemplateColumn DataField="ServerId" UniqueName="ServerId" HeaderText="Server Hosted" EditFormColumnIndex="1">
<EditItemTemplate>
<asp:DropDownList ID="ddlServerHosted" runat="server" DataTextField="Servers.ServerName" DataValueField="ServerId" Width="40%">
</asp:DropDownList>
</EditItemTemplate>
</telerik:GridTemplateColumn>
</Columns>
<EditFormSettings ColumnNumber="2" CaptionDataField="AppId" InsertCaption="Insert New Application" EditFormType="AutoGenerated">
<EditColumn InsertText="Insert record" EditText="Edit application id #:" EditFormColumnIndex="0" UpdateText="Application updated" UniqueName="InsertCommandColumn1" CancelText="Cancel insert" ButtonType="ImageButton"></EditColumn>
<FormTableItemStyle Wrap="false" />
<FormTableStyle GridLines="Horizontal" CellPadding="2" CellSpacing="0" Height="110px" Width="110px" />
<FormTableAlternatingItemStyle Wrap="false" />
<FormStyle Width="100%" BackColor="#EEF2EA" />
<FormTableButtonRowStyle HorizontalAlign="Right" />
</EditFormSettings>
</MasterTableView>
</telerik:RadGrid>
<asp:EntityDataSource ID="applicationsEntityDataSource" runat="server"
ConnectionString="name=AnalyticsEntities" EnableDelete="True"
EntityTypeFilter="Applications" EnableInsert="True" EnableUpdate="True" EntitySetName="Applications"
DefaultContainerName="AnalyticsEntities" Include="Servers">
</asp:EntityDataSource>
I tried another approach where I replaced the GridTemplateColumn with the following code
<telerik:RadComboBox ID="RadComboBox1" DataSourceID="serversEntityDataSource" DataTextField="ServerName" DataValueField="ServerId" AppendDataBoundItems="true" runat="server" >
<Items>
<telerik:RadComboBoxItem />
</Items>
and using a separate EntityDataSource control as follows:
<asp:EntityDataSource ID="serversEntityDataSource" runat="server"
ConnectionString="name=AnalyticsEntities" EnableDelete="True"
EntityTypeFilter="Servers" EnableInsert="True" EnableUpdate="True" EntitySetName="Servers"
DefaultContainerName="AnalyticsEntities">
</asp:EntityDataSource>
but, I get the following error.
Application cannot be inserted. Reason: Entities in 'AnalyticsEntities.Applications' participate in the 'FK_Servers_Applications' relationship. 0 related 'Servers' were found. 1 'Servers' is expected.
My question is, how do you bind the navigation property and load the values in the DropDownList/RadComboBox control?

Answer 1

I believe you bind your dropdownlist to that second datasource instead of the grid's datasource (as you did in the second example). Then you set the SelectedValue property on the dropdown/combobox using the <%# BIND("ServerId") %> syntax within the template.