Here are a few things I learned while developing for LINQ to SQL.
Associations to Views
Views can be added to the designed and manual associations can be added between them and other tables/views. However, the association will not create a parent/child property in the code unless you modify the view properties to define "primary keys".
Example: using NorthWind, create a blank LINQ-to-SQL model. Drag the Orders table and the Order_Subtotals view onto the designer, and create an association between "OrderID" on each.
Now compile – you should see a warning from the compiler that Order_Subtotal does not have primary keys and therefore the relationship could not be coded.
Solution: in Order_Subtotal object, set the IsPrimaryKey = true for column "OrderID". This will enabled the relationship to be created.