如何在EntityDataSource中处理自连接？

Question

I wonder how to handle self join in EntityDataSource .

IF I have i query like this :

SELECT b.degree_name ,c.degree_name as degree_next
FROM EMPDEGPROM a INNER JOIN  DEGREEWORK b
ON a.degree_code=b.degree_code
INNER JOIN DEGREEWORK c
ON a.next_degree_code =c.degree_code
WHERE a.emp_num=6777

---

How to use this data source as EntityDataSource.?

I try to do this but i can't get degree_next

<asp:EntityDataSource ID="EmpPromotionsDS" runat="server"
            ConnectionString="name=CTX" DefaultContainerName="CTX" EnableFlattening="False"
            EntitySetName="EMPDEGPROMs" EntityTypeFilter="EMPDEGPROM" Where="it.EMP_NUM =@emp_num"  Include="DEGREEWORK" >
            <WhereParameters>
                <asp:SessionParameter Name="emp_num" SessionField="emp_num" DbType="Int32" />
            </WhereParameters>

Answer 1

Create a view.

CREATE VIEW XXX AS
SELECT a.emp_num, b.degree_name ,c.degree_name as degree_next
FROM EMPDEGPROM a INNER JOIN  DEGREEWORK b
ON a.degree_code=b.degree_code
INNER JOIN DEGREEWORK c
ON a.next_degree_code =c.degree_code

EF has no problem reading from views.

Answer 2

• If you want only readonly, you could drop the EntitySetName, EntityTypeFilter, Where and Include properties and use instead use the CommandText property.

• If you want to use directly your entities, make sure you have a navigation property with a self reference and precise it in your include property.

 <asp:EntityDataSource ID="EmpPromotionsDS" runat="server" ConnectionString="name=CTX" DefaultContainerName="CTX" EnableFlattening="False" CommandText= SELECT b.degree_name ,c.degree_name as degree_next FROM EMPDEGPROM a INNER JOIN DEGREEWORK b ON a.degree_code=b.degree_code INNER JOIN DEGREEWORK c ON a.next_degree_code =c.degree_code WHERE a.emp_num=@EmployeeId> <CommandParameters> <asp:ControlParameter Name="EmployeeId" ControlID="EmployeeIdTextBox" Type="Int32"/> </CommandParameters>