MSDN Magazine - March 2008 - (Page 64)

Sponsored Content The ADO.NET Entity Framework The ADO.NET Entity Framework allows you to define and program against an Entity Data Model that is mapped to an underlying relational schema. The Entity Data Model may be exposed as strongly-typed business objects queried through an extended SQL grammar (EntitySQL) or Language Integrated Query (LINQ), or may be queried using traditional ADO.NET programming patterns by passing EntitySQL to an EntityClient ADO.NET Data Provider. The ADO.NET Entity Framework supports flexible mapping over relational data, providing a number of advantages over directly querying the storage schema: • The Entity Data Model represents concepts not present in the relational model. Through the Entity Data Model, applications can reason about types, inheritance, and relationships as first-class concepts, greatly reducing the complexity of queries, implicit assumptions, and data transformations hard-coded within the application. • Storage schemas don’t reflect application patterns. Storage schemas are typically, and rightly, designed around storage considerations. For example, tables are normalized to facilitate data consistency. • Storage schemas change over time. Even though a storage schema may start out perfectly normalized, it is likely to change over time based on size of data, access patterns, and maintenance requirements. For example, a DBA may partition one large table into multiple smaller tables, or denormalize data by combining tables in order to improve locality of data for common access patterns. These types of schema changes break applications that rely on the logical schema of the store. as strongly typed Business Objects, and a Metadata Runtime that provides information about types, relationships, and mapping to both the EntityClient and the ObjectServices. The relationship between these components is shown on the previous page. EntityClient Data Provider The EntityClient Data Provider is an ADO.NET Data Provider that exposes a defined conceptual Entity Data Model on top of a provider-specific ADO.NET Data Provider, such as the ADO.NET Data Provider for Microsoft SQL Server (SqlClient). The EntityClient accepts textual commands according to an EntitySQL grammar. EntitySQL extends SQL with constructs to take advantage of the richness of the Entity Data Model, such a strong notion of type and type inheritance as well as relationship navigation and complex members. Because EntityClient exposes a common data model and common command syntax on top of providerspecific ADO.NET Data Provider, it provides a high degree of interoperability across different stores and different schemas. The EntityClient consumes three distinct pieces of metadata: • Conceptual Schema (“C-Space”) describes the application schema in terms of the Entity Data Model. It is typically loaded from an XML file or stream according to a Conceptual Schema Definition Language (CSDL). • Storage Schema (“S-Space”) describes the schema of the relational store. It is typically loaded from an XML file or stream according to a Storage Schema Definition Language (SSDL). • Entity Mapping (“C-S Map”) between the Conceptual Model and the Storage Schema. It is typically loaded from an XML file or stream according to a Mapping Schema Language (MSL). Architecture The ADO.NET Entity Framework is comprised of an EntityClient ADO.NET Data Provider that exposes an Entity Data Model on top of a storage schema, a set of ObjectServices that expose the Entity Data Model

Table of Contents Feed for the Digital Edition of MSDN Magazine - March 2008

MSDN Magazine - March 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Introducing ASP.NET MVC Loosen Up CI Server Performance Office Development Test Run Security Briefs Extreme ASP.NET Foundations .NET Matters {End Bracket}

MSDN Magazine - March 2008

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