ADO.NET vNext Part 2: Using the Object Services Layer
The Entity Data Model and ADO.NET vNext let you deal with tabular data as objects, eliminating much of the effort endemic to older data-retrieval and modification code.
by Thiru Thangarathinam
December 8, 2006
he first installment of this three-part article series introduced the core concepts of ADO.NET vNext, including the Entity Data Model (EDM), Entity SQL, and the Mapping Provider. It also discussed the steps involved in executing entity SQL queries against the EDM and retrieving output in the form of rows and values (contained in a DbDataReader object). This installment builds on Part 1, focusing on a layer named the Object Services Layer that lets you work with database tables and columns as objects, and properties. The object services layer is an abstraction on top of EDM that leverages the same EDM infrastructure to execute queries against a database.
The object services layer provides a strongly typed object abstraction, letting you work with the database layer in terms of programming language objects rather than only the tabular "rows-and-columns" model thereby handling the impedance mismatch problem. The object services layer provides a cache of objects and the ability to perform CRUD operations on these objects. There are two ways to execute queries through the object services layer—via LINQ or Entity SQL. This installment focuses on query execution using Entity SQL and the next installment discusses using of LINQ for query execution in detail.
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