ASP.NET 4 Unleashed

Building Entity Associations

One entity can be associated with another entity. For example, a MovieCategory entity might be associated with one or more Movie entities.

If you have defined foreign key relationships between your database tables, these relationships are preserved when you drag your tables onto the LINQ to SQL Designer. The LINQ to SQL Designer generates entity associations based on the foreign key relationships automatically.

For example, the MovieCategory entity is related to the Movie entity through the Movie entity’s CategoryId property. As long as you have defined a foreign key relationship between Movie.CategoryId and MovieCategory.Id, you can use a query like this following:

The second statement grabs the Drama movie category. ...