%META:TOPICPARENT{name="VirtIngresEntityFrameworkUsage"}% ===Manually creating EDM Associations (FKs) for the Ingres Tutorial database=== The following steps will detail what is required to manually create **Associations** in your Entity Data Model. Before commencing the process, you will need to determine where these associations exist and their multiplicity (e.g., one-to-one, one-to-many, etc.). NOTE: These steps will need to be repeated for each association. 1. The first Association I will deal with is the relationship between cust_orders and cust_info, identified by the presence of the Scalar Property cust_no in both entities. This is a one-to-one relationship, as an entry in a customer order may only be associated with one customer's information. %BR%%BR%

%BR%%BR% 2. To add the Association, right-click on the Customer entity. Then, click **Add** -> **Association**. %BR%%BR%

%BR%%BR% 3. You will now see the **Add Association** dialog. %BR%%BR%

%BR%%BR% 4. Hit **OK**. The diagram will be refreshed to include the newly created association.%BR%%BR% 5. You now need to edit the mappings associated with the newly created association, so right-click the association on the diagram and select **Table Mapping** to display the **Mapping Details** pane. %BR%%BR%

%BR%%BR% 6. Click the line that reads <Add a Table or View> to reveal a drop down list of all entities. %BR%%BR%

%BR%%BR% 7. Here you need to select the entity on the right/far side of the association (the entity where the foreign key exists). In this example, it is the cust_orders entity. %BR%%BR%

%BR%%BR% 8. The **Mapping Details** pane now refreshes to display both ends of the association. You will now be required to provide relevant target store data types in the **Column** column for the key fields, as depicted here. %BR%%BR%

%BR%%BR% 9. Once the mapping is complete, you can build the project using **Build** -> **Build Solution**. NOTE: It is worthwhile to (re)build as each association is made, since the error messages can be a little confusing. %BR%%BR%

%BR%%BR% 10. This should result in the following error, which is included here, since I (the author) found it misleading. %BR%%BR%

%BR%%BR% This error indicates that there are two sources — in this case, the cust_orders entity's Scalar Property cust_no and the Navigation Property cust_info in — which are being mapped to the same target column — the Ingres column cust_orders.cust_no — which is not supported. %BR%%BR%

%BR%%BR% 11. The solution is simple! Delete the mapping for Scalar Property cust_orders.cust_no. Its only purpose is to hold data representing a relationship/association (it is a Foreign Key), which has already been represented by the newly-created association and resulting Navigation Property cust_no.%BR%%BR% Right-click on cust_orders.cust_no. Then, click **Delete**. %BR%%BR%

%BR%%BR% 12. The model diagram will refresh to reflect this change. %BR%%BR%

%BR%%BR% 13. Build the project, again, using **Build** -> **Build Solution**. %BR%%BR%

%BR%%BR% 14. The project should now build fine. %BR%%BR%

%BR%%BR% You will need to repeat these steps for each association until you have a completed Entity Data Model. %BR%%BR%

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