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Entity Framework: Self-Tracking Entities

December 6, 2011 Leave a comment

Working with Self-Tracking Entities

In an Entity Framework application, an object context is responsible for tracking changes in the entities in an object graph. However, in N-tier scenarios, the object context might not be available on the tier that modifies the entities. Starting with the .NET Framework version 4, self-tracking entities can help you track changes in any tier.

NOTE: Use self-tracking entities only if the object context is not available on a tier where the changes to the object graph are made. If the object context is available, use EntityObject derived types, or “plain-old” CLR objects (POCO) types, or POCO proxy types.

Starting with Microsoft Visual Studio 2010, the ADO.NET Self-Tracking Entity Generator template generates self-tracking entities. This template item generates two .tt (text template) files: .tt and .Context.tt. The .tt file generates the entity types and a helper class that contains the change-tracking logic that is used by self-tracking entities and the extension methods that allow setting state on self-tracking entities. The .Context.tt file generates a typed ObjectContext and an extension class that contains ApplyChanges methods for the ObjectContext and ObjectSet classes. These methods examine the change-tracking information that is contained in the graph of self-tracking entities to infer the set of operations that must be performed to save the changes in the database.

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