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WCF 4.5 Multi-Layer Services Development with Entity Framework by Mike Liu

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Deferred (lazy) loading versus eager loading

In one of the above 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 Products and Category tables. In the Northwind.edmx design pane, click on the line that connects the Products table and the Categories table, and you will see all of the properties of the association. Note that its Referential Constraint properties are Category.CategoryID -> Product.CategoryID, meaning that category ID is the key field to link these two tables.

Because of this association, we can ...

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