Book Image

Mastering Entity Framework Core 2.0

By : Prabhakaran Anbazhagan
Book Image

Mastering Entity Framework Core 2.0

By: Prabhakaran Anbazhagan

Overview of this book

Being able to create and maintain data-oriented applications has become crucial in modern programming. This is why Microsoft came up with Entity Framework so architects can optimize storage requirements while also writing efficient and maintainable application code. This book is a comprehensive guide that will show how to utilize the power of the Entity Framework to build efficient .NET Core applications. It not only teaches all the fundamentals of Entity Framework Core but also demonstrates how to use it practically so you can implement it in your software development. The book is divided into three modules. The first module focuses on building entities and relationships. Here you will also learn about different mapping techniques, which will help you choose the one best suited to your application design. Once you have understood the fundamentals of the Entity Framework, you will move on to learn about validation and querying in the second module. It will also teach you how to execute raw SQL queries and extend the Entity Framework to leverage Query Objects using the Query Object Pattern. The final module of the book focuses on performance optimization and managing the security of your application. You will learn to implement failsafe mechanisms using concurrency tokens. The book also explores row-level security and multitenant databases in detail. By the end of the book, you will be proficient in implementing Entity Framework on your .NET Core applications.
Table of Contents (20 chapters)
Title Page
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Dedication
Preface
4
Building Relationships – Understanding Mapping

Enhancing queries with expression trees


An expression tree is a mechanism that allows developers to create expressions that are necessary for the filters in the queries. In .NET, we have Func<T, TResult> to wrap a Where predicate and use it in multiple occurrences. We could use the same mechanism to create expression trees and leverage them in query objects.

The generic IQueryExpression interface has a provision to create an expression through Func, the following code creates contract for AsExpression().

public interface IQueryExpression<T>
    {
      Expression<Func<T, bool>> AsExpression();
    }

The concrete expression class implements IQueryExpression with concrete methods and their interface counterpart and wraps the Where predicate inside the AsExpression method, which returns a Func object. The following code provides a wildcard search on all fields from the Post entity using the expression approach:

    public class GetPaginatedPostByKeywordQueryExpression :...