Create a referential constraint for the SalesOrder_SalesOrderItem association. A referential constraint is similar to a relational database table foreign key, defining relationships between and within tables.

1. Double-click the Referential Constraint node under the SalesOrder_SalesOrderItem association.
2. In the right pane, click Append Row and select the SoID value for the Principal Key and also for the Dependent Property, then click Enter.
   All other fields are automatically populated.
   

   

   
   
3. Save your project.