asp.net entity framework <%# Bind(“linkedTable.Field”) %>

问题

.NET 4 ASP.NET

I have a DetailsView that is displaying an entity framework record for a table that has a linked lookup table. I have an asp:BoundField with the datafield set as "linkedTable.Field" and it displays a value.

<asp:BoundField DataField="linkedTable.Field" HeaderText="linkedTable.Field" 
            SortExpression="linkedTable.Field" />

I am trying to use that value in an asp:TemplateField but when I try to get it using:

<asp:TemplateField HeaderText="Field" SortExpression="linkedTable.Field" >
   <EditItemTemplate>
     <asp:Label runat="server" ID="lblField" Text='<%# Bind("linkedTable.Field") %>' />
   </EditItemTemplate>
</asp:TemplateField>

Nothing shows up in the label. I can change the Bind() to a field that is not part of the linked table and it works (i.e. the "ID" field). My problem is I don't understand why the linkedtable.Field value shows up in one context and not in the other.

FYI, my data connection is a EntityDataSource

<asp:EntityDataSource ID="edsNYSEDaily" runat="server" 
    ConnectionString="name=ServerDBEntities" 
    DefaultContainerName="ServerDBEntities" EntitySetName="tblNYSE" 
    EntityTypeFilter="tblNYSE" EnableUpdate="True" EnableFlattening="true"
    AutoGenerateWhereClause="True" Select="" Where="">
    <WhereParameters>
        <asp:QueryStringParameter DefaultValue="0" Name="ID" 
            QueryStringField="ID" Type="Int32" />
    </WhereParameters>

Let me know if you need any other information. I am stuck

回答1:

Ok, discovered the problem:
Needed to add Include="linkedTable" to the EntityDataSource tag. Still not sure why it was even working in the <asp:DataBound /> tag.

Source for the answer: forums.asp.net

Copy of the text:

you should start here: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.entitydatasource.include.aspx

notice that, you won't be able to Bind (I mean two-way data-binding) the related entities (see the remarks there).

and, you'd have to use a TemplateField for those properties.

see this example (I used the link table 'TableAB' for EntitySetName and included the other two):

    <asp:GridView ID="GridView1" runat="server" AllowPaging="True" AllowSorting="True"
        AutoGenerateColumns="False" DataKeyNames="ID" DataSourceID="EntityDataSource1">
        <Columns>
            <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" />
            <asp:BoundField DataField="ID" HeaderText="ID" ReadOnly="True" SortExpression="ID" />
            <asp:BoundField DataField="IDA" HeaderText="IDA" SortExpression="IDA" />
            <asp:BoundField DataField="IDB" HeaderText="IDB" SortExpression="IDB" />
            <asp:TemplateField HeaderText="TableA Name">
                <ItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Eval("TableA.NameA") %>' />
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="TableB Name">
                <ItemTemplate>
                    <asp:Label ID="Label2" runat="server" Text='<%# Eval("TableB.NameB") %>' />
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <asp:EntityDataSource ID="EntityDataSource1" runat="server" ConnectionString="name=ABLinkEntities"
        DefaultContainerName="ABLinkEntities" EnableDelete="True" EnableFlattening="False"
        EnableInsert="True" EnableUpdate="True" EntitySetName="TableABs" Include="TableA,TableB">
    </asp:EntityDataSource>

you'll have to re-consider the updates and deletes, you could do them manually.

来源：https://stackoverflow.com/questions/9730498/asp-net-entity-framework-bindlinkedtable-field