Book Image

Entity Framework Tutorial (Update) - Second Edition

By : Joydip Kanjilal
Book Image

Entity Framework Tutorial (Update) - Second Edition

By: Joydip Kanjilal

Overview of this book

The ADO.NET Entity Framework from Microsoft is a new ADO.NET development framework that provides a level of abstraction for data access strategies and solves the impedance mismatch issues that exist between different data models This book explores Microsoft’s Entity Framework and explains how it can used to build enterprise level applications. It will also teach you how you can work with RESTful Services and Google’s Protocol Buffers with Entity Framework and WCF. You will explore how to use Entity Framework with ASP.NET Web API and also how to consume the data exposed by Entity Framework from client applications of varying types, i.e., ASP.NET MVC, WPF and Silverlight. You will familiarize yourself with the new features and improvements introduced in Entity Framework including enhanced POCO support, template-based code generation, tooling consolidation and connection resiliency. By the end of the book, you will be able to successfully extend the new functionalities of Entity framework into your project.
Table of Contents (16 chapters)
Entity Framework Tutorial Second Edition
About the Author
About the Reviewers

Attaching and detaching objects to and from ObjectContext

You can use the Attach or Detach methods of the ObjectContext class to attach or detach objects. It should be noted that Attach will attach the entire object graph. The method cannot determine which objects are new and which already exist in ObjectContext. Note that when you execute a query on ObjectContext, the objects that are returned as a result of the query are attached in ObjectContext.

You can attach an object to ObjectContext by calling any of the following methods on ObjectContext:

  • Attach

  • AddObject

  • AttachTo

  • ApplyPropertyChanges

But what does Attach and Detach mean here? You use Attach to attach an object to the context. You should use Attach when the entity already exists in the database and you want the context to know about it without performing a query to locate the entity. When you attach an entity to ObjectContext using the Attach method, it sets EntityState of the object being attached to the Unchanged state. In...