ADO.NET Entity Framework

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ADO.NET Entity Framework
Deyan Varchev
General Manager Avaxo Ltd.
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What Is It?

• The ADO.NET Entity Framework is part of
  Microsofts next generation of .NET technologies.
• It is intended to make it easier and more
  effective for object-oriented applications to
  work with data.

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The Problem Being Addressed

• Inherit differences between data expression in a
  relational database and the same data expressed
  in an object-oriented application.

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The Logical Data Model

• Almost any business application today has to
  speak to a relational database.
• This involves the usual suspects of tables with
  foreign keys, a smattering of views, and
  generally a gob of stored procedures.

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The Object-Oriented Domain Model

• Applications themselves are written in a
  completely different world.
• The same data that lives in the relational
  database is represented entirely differently in
  the application.

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The Result

• The result of this impedance mismatch is that
  developers devote a lot of time and energy
  writing code to translate between how the
  database likes to see data and how the
  application likes to see data.

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Other Ways to Address The Same Problem

• Hibernate (Java)
• Enterprise Objects Framework (Mac OS)
• NHibernate (.NET)
• LINQ to SQL (Visual Studio 2008)
• And many, many, more

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The ADO.NET Entity Framework

• The ADO.NET Entity Framework seeks to remedy the
  problem by providing a layer of abstraction
  between the logical data model and the
  application domain.

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Why the Entity Model?

• Closer to the application problem space
• Better suited for object oriented programming
• Supports Inheritance
• Supports complex types
• Relationships are more meaningful to the
  application

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The Stuff in ADO.NET Entity Framework

• The tools and technology that developers will
  interact with when using the ADO.NET Entity
  Framework

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Entity Data Model

• A gob of XML that defines
• Logical Data Tables, Views, Foreign Keys
• Entity Objects that Map to the Logical Data
• The Mapping Between the Two

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Entity Data Model Designer

• A Visual Studio Designer that protects developers
  from the XML that is the EDM

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ObjectContext

• A code-generated data context created from the
  Entity Data Model
• Responsible for managing communication between
  the conceptual data model and the logical data
  model

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Entities

• Code-generated class definitions for objects
  defined in the EDM.

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Getting the Data Out

• How do we get data out of the fancy Entity Data
  Model?

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eSQL (Entity SQL)

• A brand new SQL language to learn
• Leverages the rich, object-oriented Entity Data
  Model
• Inheritance
• Collections
• Complex Types
• Literal Strings No Compiler Checking
• Questionable value in embedded SQL in code

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Extensions Methods and String Predicates

• Queries the object model created against the EDM
• Still string-based. No compiler checking
• An ugly mix of code and eSQL statements

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LINQ to Entities

• Full compiler checking. No wondering if the
  query is valid.
• A fun new SQL-Like syntax
• More OO-ish

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What Can You Do?

• The power of the Entity Data Model contrasted to
  a logical data model of tables and stored
  procedures.

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Combine Multiple Logical Tables into One Entity

• Database Tables

• Entity Data Model

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Implement Inheritance

• Database Tables

• Entity Data Model

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Other Fun Stuff

• Implement Complex Types (e.g. Address)
• Consume Conceptual Model with Reporting Services
  and other BI Tools
• Create an EDM that talks to stored procedures
• Use transactions, manage concurrency, cache
  execution plans

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Manipulate Data By Manipulating Objects
Database Result Desired EDM Object Manipulation
INSERT ROW Create new object Add object to EDM Context Update Context
DELETE ROW Get instance of object from EDM Context Ask Context to remove the object Update Context
UPDATE ROW Get instance of object from EDM Context Update object Update Context
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Lecture Topic

• Questions?