In one of the preceding examples, we retrieved the category name of a product using the following expression:
p.Category.CategoryName == "Beverages"
Even though there is no field called
categoryname in the
Products table, we can still get the category name of a product because there is an association between the
Category tables. In the Northwind.edmx design pane, click on the line that connects the Products and Categories tables and you will see all of the properties of the association. Note that its
Referential Constraint property is
Category.CategoryID -> Product.CategoryID, meaning that
category ID is the key field to link these two tables.
Because of this association, we can ...