Book Image

Entity Framework Core Cookbook - Second Edition

By : Ricardo Peres
Book Image

Entity Framework Core Cookbook - Second Edition

By: Ricardo Peres

Overview of this book

Entity Framework is a highly recommended Object Relation Mapping tool used to build complex systems. In order to survive in this growing market, the knowledge of a framework that helps provide easy access to databases, that is, Entity Framework has become a necessity. This book will provide .NET developers with this knowledge and guide them through working efficiently with data using Entity Framework Core. You will start off by learning how to efficiently use Entity Framework in practical situations. You will gain a deep understanding of mapping properties and find out how to handle validation in Entity Framework. The book will then explain how to work with transactions and stored procedures along with improving Entity Framework using query libraries. Moving on, you will learn to improve complex query scenarios and implement transaction and concurrency control. You will then be taught to improve and develop Entity Framework in complex business scenarios. With the concluding chapter on performance and scalability, this book will get you ready to use Entity Framework proficiently.

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Entity Framework Core Cookbook - Second Edition
Ricardo Peres
Nov, 2016 | 324 pages
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Table of Contents (15 chapters)
Entity Framework Core Cookbook - Second Edition
Entity Framework Core Cookbook - Second Edition
Credits
Credits
About the Author
About the Author
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Improving Entity Framework in the Real World
Improving Entity Framework in the Real World
Introduction
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
2
Mapping Entities
Mapping Entities
Introduction
Mapping non-public members
Mapping interfaces
Shadow properties
Creating one-to-one maps
Creating one-to-many maps
Creating many-to-many maps
Creating custom conventions
Using sequence key generators
Using GUIDs as keys
Implementing inheritance – Table per Class hierarchy
3
Validation and Changes
Validation and Changes
Introduction
Validating simple properties
Validating the whole entity
Validating groups of entities
Intercepting saving changes
Intercepting property changes
Setting the state of an entity
Improving MVC UI with entity framework validation
Inserting, updating, and deleting entities with stored procedures
Updating the database from model changes
Dumping the SQL script for the database creation
4
Transactions and Concurrency Control
Transactions and Concurrency Control
Introduction
Using explicit transactions
Using transactions in custom SQL operations
Implementing optimistic concurrency in SQL Server
Implementing optimistic concurrency in a database-agnostic way
5
Querying
Querying
Introduction
Executing client-side functions in LINQ queries
Mixing SQL with LINQ queries
Getting entities from the local cache
Creating filtered collections
Creating reusable queries
Querying shadow properties
Implementing the query object pattern
Using dynamic LINQ
6
Advanced Scenarios
Advanced Scenarios
Introduction
Generating entities from the database
Implementing multitenancy
Strongly typed bulk operations
Handling soft deletes
Adding logging
Capturing the audit data
Retrieving entity metadata
Improving MVC applications
Hooking infrastructure services
Using other databases
7
Performance and Scalability
Performance and Scalability
Introduction
Improving the performance of queries
Testing and profiling queries
Using asynchronous operations
Eager loading
Using the cache
Pitfalls
Pitfalls
Introduction
GroupBy executes on the client side
Table per class hierarchy requires nullable columns for derived classes
References not eagerly fetched are lost
Date/time operations are not supported
Paging in SQL Server earlier than 2012
Database null semantics
Migrations and contexts with parameterized constructors
Migrations with contexts in different projects
Accessing the service provider too soon
Setting the maximum string length
Mapping discriminator columns
Composite primary keys
Refreshing entities
Cascading entity deletes
Index
Index

Setting the state of an entity

Normally, Entity Framework knows two kinds of entities:

  • Those that have been loaded through it, such as the result of a LINQ query

  • Those that have been added to it

However, things can get more complicated; imagine, for a second, that you loaded one or more entities from a context in an ASP.NET web application and you stored them in the ASP.NET session. Because your DbContext normally only lives for the duration of an HTTP request, in the next request, you will get another one, which knows nothing about these entities. Another example would be if you loaded an entity from a query and accidentally made changes to it that you don't want to persist.

The solution for both these cases is to change the Entity Framework's perceived state of the entity (or entities). Let's see how this can be done.

Getting ready

We will be using NuGet Package Manager to install the Entity Framework Core 1 package, Microsoft.EntityFrameworkCore. We will also be using a SQL Server database...

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