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WCF 4.0 Multi-tier Services Development with LINQ to Entities

You're reading from   WCF 4.0 Multi-tier Services Development with LINQ to Entities Build SOA applications on the Microsoft platform with this hands-on guide updated for VS2010

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Product type Paperback
Published in Jun 2010
Publisher Packt
ISBN-13 9781849681148
Length 348 pages
Edition 1st Edition
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Author (1):
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Mike Liu Mike Liu
Author Profile Icon Mike Liu
Mike Liu
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Table of Contents (16) Chapters Close

WCF 4.0 Multi-tier Services Development with LINQ to Entities
Credits
About the Author
About the Reviewers
Preface
1. Introducing Web Services and Windows Communication Foundation 2. Implementing a Basic HelloWorld WCF Service FREE CHAPTER 3. Hosting and Debugging the HelloWorld WCF Service 4. Implementing a WCF Service in the Real World 5. Adding Database Support and Exception Handling to the RealNorthwind WCF Service 6. LINQ—Language Integrated Query 7. LINQ to Entities: Basic Concepts and Features 8. LINQ to Entities: Advanced Concepts and Features 9. Applying LINQ to Entities to a WCF Service 10. Distributed Transaction Support of WCF Index

Deferred (lazy) loading versus eager loading


In one of the above examples we retrieved the category name of a product using this expression:

p.Category.CategoryName == "Beverages"

Even though there is no field called categoryname in the Products table we can still get the category name of a product because there is an association between the Products and Category tables. In the Northwind.edmx design pane, click on the line that connects the Products table and the Categories table and you will see all of the properties of the association. Note that its Referential Constraint properties are Category.CategoryID -> Product.CategoryID, meaning that category ID is the key field to link these two tables.

Because of this association we can retrieve the category for each product and also retrieve products for each category.

Lazy loading by default

However, even with an association the associated data is not loaded when the query is executed. For example, suppose we use the following test method to...

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