Book Image

Functional C#

Book Image

Functional C#

Overview of this book

Functional programming makes your application faster, improves performance, and increases your productivity. C# code is written at a higher level of abstraction, so that code will be closer to business requirements, abstracting away many low-level implementation details. This book bridges the language gap for C# developers by showing you how to create and consume functional constructs in C#. We also bridge the domain gap by showing how functional constructs can be applied in business scenarios. We’ll take you through lambda expressions and extension methods, and help you develop a deep understanding of the concepts and practices of LINQ and recursion in C#. By the end of the book, you will be able to write code using the best approach and will be able to perform unit testing in functional programming, changing how you write your applications and revolutionizing your projects.
Table of Contents (19 chapters)
Functional C#
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Separating the code from domain logic and mutable shell


Sometimes, when our code processes a business transaction, it mutates some data several times. In the world of object-oriented programming languages, this is quite a common pattern. We can then separate our code into domain logic and the mutable shell. In domain logic, we simplify the code and write the business logic in a functional way using mathematical functions. As a result, this domain logic will become easy to test. In the mutable shell, we place a mutable expression; we will do this after we finish with the business logic.

Examining the code containing side-effects

Now, let's examine the following code, which contains many side-effects that we are going to refactor, and we can find it in the DomainLogicAndMutatingState.csproj project:

public class Librarianship 
{ 
  private readonly int _maxEntriesPerFile; 
  public Librarianship( 
    int maxEntriesPerFile) 
  { 
    _maxEntriesPerFile = 
 ...