Functional C#: Embracing Functional Programming in a C# World

By Carlos Bueno

"Functional C#: Embracing Functional Programming in a C# World" is a comprehensive guide that introduces readers to functional programming concepts and techniques, with a focus on their application in C#. The book explores the benefits of functional programming and compares it with object-oriented programming. It covers the evolution of C# and its functional features, functional building blocks, data structures and patterns, and various techniques for functional programming.

The book also delves into LINQ, error handling, and asynchronous programming in a functional style. It provides an overview of popular functional programming libraries for C#, such as Language-Ext, and discusses functional design patterns. Additionally, it showcases real-world applications and case studies in web development, data processing and analysis, and game engine building.

Whether you are a beginner or an experienced developer, "Functional C#: Embracing Functional Programming in a C# World" will help you embrace functional programming concepts and techniques to build more robust, scalable, and efficient software applications.

• Language: English
• Publisher: Carlos Bueno
• Release date: Feb 6, 2024
• ISBN: 9798224893973

Carlos Bueno

Carlos Bueno is a Software Engineer, currently working at CODIT Luxembourg, and a fervent advocate of functional programming. With years of experience in software development, he constantly seeks to apply the best practices and cutting-edge techniques to create efficient, maintainable, and high-quality code. In addition to his professional pursuits, Carlos is an avid cycling enthusiast and enjoys spending his free time playing video games, participating in role-playing games, and reading about the latest advancements in programming and technology. His well-rounded interests inspire him to bring creativity and innovation to his work, making him an invaluable resource for readers looking to elevate their coding skills.

Book preview

Functional C#: Embracing Functional Programming in a C# World

––––––––

Carlos Bueno

Copyright © 2023 Carlos Bueno

All rights reserved.

––––––––

DEDICATION

––––––––

To my beloved wife Ewa Walęga-Bueno,

Your constant support and source of inspiration have been the cornerstone of this journey. Your unwavering love, encouragement, and patience have been my guiding stars, helping me navigate and overcome every challenge to make this book a reality.

Thank you for always believing in me, for your steadfast faith in my abilities, and for being the light in my darkest moments.

To my cherished children, Luiz Carlos Bueno, Gustavo Bueno, and Mikołaj Walęga-Bueno,

You are my pride and joy, the embodiments of hope and dreams for the future. Your laughter and curiosity fuel my desire to create, inspire, and dream bigger.

To my dear brother Cleber Bueno,

Your companionship and solidarity through the years have been invaluable. Your presence in my life has been a source of strength and joy, reminding me of the unbreakable bond we share.

To my beloved mother Celia Bueno and father Carlos Roberto Bueno,

Your guidance, sacrifices, and unconditional love have shaped the person I am today. You have instilled in me values and virtues that no words can fully express my gratitude for.

And to my late grandmother Anna Fantucci,

Your memory is a treasure I hold close to my heart. More than 25 years since you passed, yet your influence remains a powerful force in my life. You were the most important person in my world, a beacon of wisdom, love, and kindness. Your legacy continues to inspire and guide me every day.

This book is dedicated to all of you as a token of my profound love, gratitude, and respect. Each of you has played a significant role in this journey, and it is with immense honor that I share this achievement with you.

Carlos Bueno

––––––––

CONTENTS

Contents

Chapter 1: Introduction to Functional Programming

1.1. What is Functional Programming?

1.2. Comparing Functional and Object-Oriented Programming

Fun Examples and Analogies to Contrast OOP and FP

Key Takeaways

1.3. The Benefits of Functional Programming

Chapter 2: C# and Functional Programming: A Growing Friendship

2.1. The Evolution of C# and Its Functional Features

2.2. The C# Functional Ecosystem

2.3. Hybrid Programming: Combining OO and FP in C

When combining OO and FP in C#, consider the following guidelines:

Chapter 3: Functional Building Blocks in C

3.1. Pure Functions and Immutability - The Dynamic Duo

Pure Functions:

Advantages of pure functions:

Immutability:

Advantages of immutability:

3.2. Higher-Order Functions

The Art of Delegation

Currying: A Spicy Technique

Party Tricks with Higher-Order Functions

Map

Filter

Reduce

Higher-Order Functions: The Encore

3.3 Lambda Expressions

Lambda Expressions: A Brief History

The Art of Lambda Expressions

Lambda Expressions in Action

Event Handlers

LINQ Queries

Predicate Functions

The Limits of Lambda Expressions

Lambda Expressions

3.4 Closures

Closures: A Quick Introduction

Under the Hood: How Closures Work in C

Closures in Everyday Code

The Grand Send-Off: Onward to Functional Data Structures and Patterns

Chapter 4: Functional Data Structures and Patterns

4.1. Tuples and Records: Data’s Dynamic Duo

Tuples: Small but Mighty

Records: Immutability’s Dream Team

Tuples and Records: Unstoppable Together

4.2 Pattern Matching: A Whodunit of Code

4.3 Discriminated Unions: The Swiss Army Knife of Data Types

What’s in a Name: Introducing Discriminated Unions

A Menagerie of Types: Modeling Animals

Samples Galore: More Discriminated Union Goodness

4.4 Deconstruction

4.4.1 Deconstructing Tuples

4.4.2 Deconstructing Records

4.4.4 Deconstructing with Extension Methods

4.4.5 Deconstruction Gotchas and Tips

Chapter 5:  Currying and Partial Application: The Art of Splitting Functions

5.3. Lazy Evaluation: The Art of Procrastination

5.3.1. Using the Lazy Class

5.3.2. Lazy Sequences with LINQ

5.4. Memoization: The Art of Remembering

5.4.1. Memoizing Recursive Functions

5.4.2. Creating a Memoization Decorator

Chapter 6: LINQ: The Power of Functional Programming in C

6.1. Introduction to LINQ

6.1.1. Basic LINQ Syntax

6.2. Query Syntax vs. Method Syntax

6.2.1. Query Syntax

6.2.3 Extending LINQ with Custom Query Operators

6.2.3.1 Custom Map Operator

6.3. Common LINQ Operators

Chapter 7: Error Handling and Functional Programming

7.1. Traditional Error Handling in C#: Exceptions

7.2. The Result and Either Types

7.3. Railway-Oriented Programming

Chapter 8: Asynchronous Programming in a Functional Style

8.1. Async/Await and Task-Based Asynchronous Pattern

8.2. Asynchronous Functional Pipelines

8.3 Handling Errors Asynchronously

8.3.1 Asynchronous Error Handling with Result

8.3.2 Composing Asynchronous Functions

8.3.3 Error Handling with Parallelism

8.3.4 Retrying Asynchronous Operations

Chapter 9: Usage and Examples

9.1 Maybe Example

9.2 IEnumerable Example

9.3 Extension Methods for Task Monad

Use Case 1: Stock Data API

9.4 Semigroups

9.5 Monoids

9.6  Practical Applications

9.7  String Concatenation Monoid

9.8 List Merging Monoid

9.9 Free Monads

9.9.1 Implementing a Free Monad in C

9.9.1.1 Console Operations

9.9.1.2 Free Monad Data Structure

9.9.2 Building Programs with Free Monads

9.9.2.1 Creating the Program

Chapter 10:  Using Monads with Language-Ext

Option Monad

Either Monad

Try Monad

Task Monad

State Monad

10.3. Other Functional Libraries for C

10.3.1 FSharpx.Extras

10.3.2 CSharpFunctionalExtensions

10.3.3 FsCheck

10.3.4 MoreLINQ

10.4. MoreLINQ: Practical Examples

10.4.1 DistinctBy

10.4.2 Partition

10.4.3 TakeEvery

10.4.4 Scan

Chapter 11: Real-World Applications and Case Studies

11.1 Functional Programming in Web Development: A Sci-Fi-Inspired Adventure

Language-Ext: The Warp Drive of Functional Programming

Event Sourcing: The Temporal Prime Directive

MongoDB: The Intergalactic Database

The Wallet Agent: A Trusty Tricorder with Event Sourcing

The Functional Wallet API: Engaging Warp Speed with Event Sourcing and MongoDB

Boldly Going Forward

––––––––

Functional Fun with C#: Embracing Functional Programming in a C# World

I

ACKNOWLEDGMENTS

––––––––

I would like to express my deepest gratitude to my wife Ewa for her unwavering love, support, and patience throughout the writing of this book. Your encouragement and belief in me have been invaluable, and I could not have done this without you.

I would also like to thank my dear friend Luis Alberto for his constant encouragement, valuable feedback, and insightful discussions about software development, which have helped shape the content of this book.

A special thank you also goes to Leonardo, with whom I have had countless conversations about software development. Your ideas, feedback, and support have been invaluable in shaping my thoughts and ideas.

I am also grateful to my colleagues and friends who have supported me throughout the writing of this book, offering encouragement and advice when needed.

Last but not least, I would like to thank my readers for choosing to spend their time with this book. I hope it will be a valuable resource in your journey to embrace functional programming in a C# world.

Welcome to Functional Fun with C#: Embracing Functional Programming in a C# World!

In this book, we’ll dive deep into the world of functional programming (FP) and learn how we can harness its power in C# to write efficient, robust, and maintainable code. You might think of C# as an object-oriented (OO) language, and you’re right! However, C# has evolved over the years, steadily embracing functional programming concepts, making it a powerful hybrid language. This book will guide you through the exciting journey of discovering the functional side of C# and how to incorporate FP principles into your everyday coding.

Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions, avoiding mutable state and side effects. It has been around for decades, but it has gained traction in recent years due to its inherent advantages in dealing with concurrent and distributed systems. In the age of multicore processors and big data, functional programming is more relevant than ever.

In the early chapters, we’ll explore the fundamental concepts of functional programming and compare them with object-oriented programming. Imagine functional programming as the quiet, introverted cousin of the ever-popular object-oriented programming. While object-oriented programming loves to create objects and mingle them in intricate hierarchies, functional programming prefers to keep things simple, relying on mathematical functions and immutable data structures to get the job done. This difference in approach has profound implications on how we design, write, and reason about code.

As we delve deeper into the book,