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Entity Framework Core Cookbook - Second Edition - Ricardo Peres
Table of Contents
Entity Framework Core Cookbook - Second Edition
Credits
About the Author
About the Reviewer
www.PacktPub.com
eBooks, discount offers, and more
Why subscribe?
Preface
What this book covers
What you need for this book
Who this book is for
Sections
Getting ready
How to do it…
How it works…
There's more…
See also
Conventions
Reader feedback
Customer support
Downloading the example code
Errata
Piracy
Questions
1. Improving Entity Framework in the Real World
Introduction
Improving Entity Framework by using a code-first approach
Getting ready
How to do it…
How it works…
There's more…
Convention over configuration
Model-View-Controller
Single Responsibility Principle
Provider Model
Testing
See also
Unit testing and mocking
Getting ready
How to do it…
How it works…
There's more…
One class under test
Integration tests
Arrange, Act, Assert
Mocking
Creating databases from code
Getting ready
How to do it…
How it works…
There's more…
See also
Creating mock database connections
How to do it…
How it works…
See also
Implementing the repository pattern
Getting ready
How to do it…
How it works…
There's more…
Dependency Inversion Principle
Repository and caching
Mocking
Where generic constraint
See also
Implementing the unit of work pattern
Getting ready
How to do it…
How it works…
There's more…
Call per change
Interface Segregation Principle
Refactoring
See also
2. Mapping Entities
Introduction
Mapping non-public members
Getting ready
How to do it…
How it works…
There's more…
See also
Mapping interfaces
Getting ready
How to do it…
How it works…
See also
Shadow properties
Getting ready
How to do it…
How it works…
See also
Creating one-to-one maps
Getting ready
How to do it…
How it works…
There's more…
See also
Creating one-to-many maps
Getting ready
How to do it…
How it works…
There's more…
See also
Creating many-to-many maps
Getting ready
How to do it…
How it works…
There's more…
See also
Creating custom conventions
Getting ready
How to do it…
How it works…
There's more…
See also
Using sequence key generators
Getting ready
How to do it…
How it works...
There's more…
See also
Using GUIDs as keys
Getting ready
How to do it…
How it works…
There's more…
See also
Implementing inheritance – Table per Class hierarchy
Getting ready
How to do it…
How it works…
There's more…
3. Validation and Changes
Introduction
Validating simple properties
Getting ready
How to do it…
How it works…
There's more…
See also
Validating the whole entity
Getting ready
How to do it…
How it works…
See also
Validating groups of entities
How to do it…
How it works…
See also
Intercepting saving changes
Getting ready
How to do it…
How it works…
See also
Intercepting property changes
Getting ready
How to do it…
How it works…
See also
Setting the state of an entity
Getting ready
How to do it…
How it works…
There's more…
See also
Improving MVC UI with entity framework validation
Getting ready
How to do it…
How it works…
There's more…
Understanding the HTML helper
See also
Inserting, updating, and deleting entities with stored procedures
Getting ready
How to do it…
How it works…
There's more…
See also
Updating the database from model changes
Getting ready
How to do it…
How it works…
There's more…
See also
Dumping the SQL script for the database creation
Getting ready
How to do it…
How it works…
There's more…
See also
4. Transactions and Concurrency Control
Introduction
Using explicit transactions
Atomic
Consistent
Isolation
Durability
Getting ready
How to do it…
How it works…
See also
Using transactions in custom SQL operations
Getting ready
How to do it…
How it works…
There's more…
See also
Implementing optimistic concurrency in SQL Server
Getting ready
How to do it…
How it works…
There's more…
Database wins
Client wins/last one wins
See also
Implementing optimistic concurrency in a database-agnostic way
Getting ready
How to do it…
How it works…
There's more…
See also
5. Querying
Introduction
Executing client-side functions in LINQ queries
Getting ready
How to do it…
How it works…
See also
Mixing SQL with LINQ queries
Getting ready
How to do it…
How it works…
There's more…
See also
Getting entities from the local cache
Getting ready
How to do it…
How it works…
There's more…
See also
Creating filtered collections
Getting ready
How to do it…
How it works…
There's more…
See also
Creating reusable queries
Getting ready
How to do it…
How it works…
There's more…
Extension methods
Naming conflict
See also
Querying shadow properties
Getting ready
How to do it…
How it works…
There's more…
See also
Implementing the query object pattern
Getting ready
How to do it…
How it works…
There's more…
See also
Using dynamic LINQ
Getting ready
How to do it…
How it works…
There's more…
6. Advanced Scenarios
Introduction
Generating entities from the database
Getting ready
How to do it…
How it works…
There's more…
Implementing multitenancy
Getting ready
How to do it…
How it works…
There's more…
Strongly typed bulk operations
Getting ready
How to do it…
How it works…
There's more…
Handling soft deletes
Getting ready
How to do it…
How it works…
See also
Adding logging
Getting ready
How to do it…
How it works…
There's more…
Capturing the audit data
Getting ready
How to do it…
How it works…
See also
Retrieving entity metadata
Getting ready
How to do it…
How it works…
There's more…
See also
Improving MVC applications
Getting ready
How to do it.…
See also
Hooking infrastructure services
Using other databases
How to do it…
7. Performance and Scalability
Introduction
Improving the performance of queries
Getting ready
How to do it…
Modifications
Updates
Deletes
Queries
SQL
LINQ
See also
Testing and profiling queries
How to do it…
Logging
Database profiler
Real time monitoring
Testing
See also
Using asynchronous operations
Getting ready
How to do it…
Queries
Modifications
See also
Eager loading
Getting ready
How to do it…
How it works…
See also
Using the cache
Getting ready
How to do it…
How it works…
There's more…
A. Pitfalls
Introduction
GroupBy executes on the client side
Problem
How to fix it…
Table per class hierarchy requires nullable columns for derived classes
Problem
How to solve it…
References not eagerly fetched are lost
Problem
How to solve it…
Date/time operations are not supported
Problem
How to solve it…
Paging in SQL Server earlier than 2012
Problem
How to solve it…
Database null semantics
Problem
How to solve it…
Migrations and contexts with parameterized constructors
Problem
How to solve it…
Migrations with contexts in different projects
Problem
How to solve it…
Accessing the service provider too soon
Problem
How to solve it…
Setting the maximum string length
Problem
How to solve it…
Mapping discriminator columns
Problem
How to solve it…
Composite primary keys
Problem
How to solve it…
Refreshing entities
Problem
How to solve it…
Cascading entity deletes
Problem
How to solve it…
Index
Entity Framework Core Cookbook - Second Edition
Entity Framework Core Cookbook - Second Edition
Copyright © 2016 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.
First published: March 2012
Second edition: November 2016
Production reference: 1031116
Published by Packt Publishing Ltd.
Livery Place
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Birmingham B3 2PB, UK.
ISBN 978-1-78588-330-9
www.packtpub.com
Credits
Author
Ricardo Peres
Reviewer
Jason De Oliveira
Commissioning Editor
Kunal Parikh
Acquisition Editor
Chaitanya Nair
Content Development Editors
Siddhi Chavan
Merint Mathew
Technical Editors
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Proofreader
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Indexer
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Graphics
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Cover Work
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About the Author
Ricardo Peres is a Portuguese developer, blogger, and occasionally an e-book author. He has more than 17 years of experience in software development, using technologies such as C/C++, Java, JavaScript, and .NET. His interests include distributed systems, architectures, design patterns, and general .NET development.
He currently works for London-based Simplifydigital as a technical evangelist, and was first awarded as MVP in 2015.
Ricardo maintains a blog, Development With A Dot, where he regularly writes about technical issues. You can read it here: http://weblogs.asp.net/ricardoperes.
He has reviewed Learning NHibernate 4 for Packt.
You can catch up with him at @RJPeres75.
I'd like to thank my family, Zézinha, Francisco, and Madalena, for their love and patience and my friends and colleagues at Simplifydigital for all their support.
This book is dedicated to my parents, Irene (1947-2005) and Jorge Peres (1941-2015), with love and saudades.
About the Reviewer
Jason De Oliveira works as a CTO for MEGA International (http://www.mega.com), a software company in Paris (France) that provides modeling tools for enterprise architecture, enterprise governance risk, and compliance management. He is an experienced manager and senior solutions architect with a lot of skills in software architecture and enterprise architecture.
He loves sharing his knowledge and experience via his blog, by speaking at conferences, writing technical books, writing articles in the technical press, giving software courses as MCT, and coaching co-workers in his company. He frequently collaborates with Microsoft, and you can quite often find him at the Microsoft Technology Center (MTC) in Paris. Microsoft awarded him in 2011 with an MVP in C# for his numerous contributions to the Microsoft community. Microsoft seeks to recognize the best and brightest from technology communities around the world with the MVP award. These exceptional and highly-respected individuals come from more than 90 countries, serve their local online and offline communities, and have an impact worldwide. Jason is very proud to be one of them. Please feel free to contact him via his blog (http://www.jasondeoliveira.com) if you need any technical assistance or want to discuss technical subjects.
Jason has worked as a reviewer on .NET 4.5 Expert Programming Cookbook, WCF 4.5 Multi-tier Services Development with LINQ to Entities, .NET 4.5 Parallel Extensions Cookbook, and WCF 4.5 Multi-layer Services Development with Entity Framework, Third Edition by Packt. He has also worked as an author on Visual Studio 2013: Concevoir, développer et gérer des projets Web, les gérer avec TFS 2013 by Editions ENI.
I would like to thank my lovely wife, Orianne, and my beautiful daughters, Julia and Léonie, for supporting me in my work and for accepting long days and short nights during the week and sometimes even during the weekend. My life would not be the same without them!
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Preface
This book is about the new Entity Framework Core 1.0. In here, you will find recipes that will hopefully make your life easier when working with Entity Framework Core. If all goes well, you will also have some fun while doing it.
It has something for both beginners as well as more seasoned developers.
What this book covers
Chapter 1, Using Entity Framework in the Real World, introduces you to the structure of the sample project, and we will see some examples of how to use Entity Framework in a real MVC application.
Chapter 2, Mapping Entities, presents the way to configure the mapping of entities and properties and relations between entities.
Chapter 3, Validation and Changes, talks about how Entity Framework detects modifications made to entities, and how we can intercept those modifications, or apply our custom validation logic to it.
Chapter 4, Transactions and Concurrency Control, covers ACID transactions and optimistic concurrency control.
Chapter 5, Querying, covers the many querying options available to Entity Framework Core, some of which are quite new.
Chapter 6, Advanced Scenarios, presents some more advanced scenarios.
Chapter 7, Performance and Scalability, introduces you to some tips related to how we can make our application more responsive and scalable.
Appendix, Pitfalls, presents a list of pitfalls, or anti-patterns, regarding Entity Framework Core usage.
What you need for this book
All you need is .NET Core, including Entity Framework Core, together with an edition of Visual Studio 2015 that supports it (the free Community Edition will work).
We will be using SQL Server as the relational database (any version starting with 2012 will do, in any edition), including Express.
Who this book is for
This book is for .NET developers who work with relational databases on a daily basis and understand the basics of Entity Framework, but now want to use it in a more efficient manner. You are expected to have some prior knowledge of Entity Framework.
Sections
In this book, you will find several headings that appear frequently (Getting ready, How to do it, How it works, There's more, and See also).
To give clear instructions on how to complete a recipe, we use these sections as follows:
Getting ready
This section tells you what to expect in the recipe, and describes how to set up any software or any preliminary settings required for the recipe.
How to do it…
This section contains the steps required to follow the recipe.
How it works…
This section usually consists of a detailed explanation of what happened in the previous section.
There's more…
This section consists of additional information about the recipe in order to make the reader more knowledgeable about the recipe.
See also
This section provides helpful links to other useful information for the recipe.
Conventions
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: Create an entity with the name MyEntity in the BusinessLogic project.
A block of code is set as follows:
namespace BusinessLogic
{
public class Post : BlogContent
{
public string Body { get; set; }
}
}
When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:
namespace BusinessLogic
{
public class Post : BlogContent
{
public string Body { get; set; }
}
}
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Open Using EF Core Solution from the included source code examples.
Note
Warnings or important notes appear in a box like this.
Tip
Tips and tricks appear like this.
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Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of.
To send us general feedback, simply e-mail <[email protected]>, and mention the book's title in the subject of your message.
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Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.
Downloading the example code
You can download the example code files for this book from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.
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Errata
Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you could report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting http://www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded to our website or added to any list of existing errata under the Errata section of that title.
To view the previously submitted errata, go to https://www.packtpub.com/books/content/support and enter the name of the book in the search field. The required information will appear under the Errata section.
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Piracy of copyrighted material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works in any form on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy.
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Questions
If you have a problem with any aspect of this book, you can contact us at <[email protected]>, and we will do our best to address the problem.
Chapter 1. Improving Entity Framework in the Real World
In this chapter, we will cover the following topics:
Improving Entity Framework by using a code-first approach
Unit testing and mocking
Creating databases from code
Creating mock database connections
Implementing the repository pattern
Implementing the unit of work pattern
Introduction
If we were to buy the materials to build a house, would we buy the bare minimum to get four walls up and a roof, without a kitchen or a bathroom? Or would we buy enough material to build the house with multiple bedrooms, a kitchen, and multiple bathrooms?
The problem lies in how we define the bare minimum. The progression of software development has made us realize that there are ways of building software that do not require additional effort, but reap serious rewards. This is the same choice we are faced with when we decide on the approach to take with Entity Framework. We could just get it running and it would work most of the time.
Customizing and adding to it later would be difficult, but doable. There are a few things that we would need to give up for this approach. The most important among those is control over how the code is written. We have already seen that applications grow, mature, and have features added. The only thing that stays constant is the fact that at some point in time, in some way, we will come to push the envelope of almost every tool that we leverage to help us. The other side is that we could go into development, being aware of the value-added benefits that cost nothing, and with that knowledge, avoid dealing with unnecessary constraints.
When working with Entity Framework, there are some paths and options available to us. There are two main workflows for working with Object-Relational Mapper (ORM) tools such as Entity Framework:
Database first: We start by defining our database objects and their relations, then write our classes to match them, and we bind them together
Code first: We start by designing our classes as Plain Old CLR Objects (POCOs) to model the concepts that we wish to represent, without caring (too much!) how they will be persisted in the database
Note
The model-first approach was dropped in Entity Framework Core 1.0.
While following the database-first approach, we are not concerned with the actual implementation of our classes, but merely the structures—tables, columns, keys—on which they will be persisted. In contrast, with POCOs or code first, we start by designing the classes that will be used in our programs to represent the business and domain concepts that we wish to model. This is known as Domain-Driven Design (DDD). DDD certainly includes code first, but it is much more than that.
All of these approaches will solve the problem with