Functional Programming in C# : How to Write Better C# Code

**Summary** __Functional Programming in C#__ teaches you to apply functional thinking to real-world problems using the C# language. The book, with its many practical examples, is written for proficient C# programmers with no prior FP experience. It will give you an awesome new perspective. Purchase of the print book includes a free eBook in PDF, Kindle, and ePub formats from Manning Publications. **About the Technology** Functional programming changes the way you think about code. For C# developers, FP techniques can greatly improve state management, concurrency, event handling, and long-term code maintenance. And C# offers the flexibility that allows you to benefit fully from the application of functional techniques. This book gives you the awesome power of a new perspective. **About the Book** __Functional Programming in C#__ teaches you to apply functional thinking to real-world problems using the C# language. You'll start by learning the principles of functional programming and the language features that allow you to program functionally. As you explore the many practical examples, you'll learn the power of function composition, data flow programming, immutable data structures, and monadic composition with LINQ. **What's Inside** * Write readable, team-friendly code * Master async and data streams * Radically improve error handling * Event sourcing and other FP patterns **About the Reader** Written for proficient C# programmers with no prior FP experience. **About the Author** **Enrico Buonanno** studied computer science at Columbia University and has 15 years of experience as a developer, architect, and trainer. **Table of Contents** PART 1 - CORE CONCEPTS2. Introducing functional programming 3. Why function purity matters 4. Designing function signatures and types 5. Patterns in functional programming 6. Designing programs with function composition PART 2 - BECOMING FUNCTIONAL8. Functional error handling 9. Structuring an application with functions 10. Working effectively with multi-argument functions 11. Thinking about data functionally 12. Event sourcing: a functional approach to persistence PART 3 - ADVANCED TECHNIQUES14. Lazy computations, continuations, and the beauty of monadic composition 15. Stateful programs and stateful computations 16. Working with asynchronous computations 17. Data streams and the Reactive Extensions 18. An introduction to message-passing concurrency Dedication About this Book Who should read this book How this book is organized Code conventions and downloads Book forum About the author Part 1. Core concepts Chapter 1. Introducing functional programming 1.1. What is this thing called functional programming? 1.2. How functional a language is C#? 1.3. Thinking in functions 1.4. Higher-order functions 1.5. Using HOFs to avoid duplication 1.6. Benefits of functional programming Chapter 2. Why function purity matters 2.1. What is function purity? 2.2. Purity and concurrency 2.3. Purity and testability 2.4. Purity and the evolution of computing Chapter 3. Designing function signatures and types 3.1. Function signature design 3.2. Capturing data with data objects 3.3. Modeling the absence of data with Unit 3.4. Modeling the possible absence of data with Option Chapter 4. Patterns in functional programming 4.1. Applying a function to a structure’s inner values 4.2. Performing side effects with ForEach 4.3. Chaining functions with Bind 4.4. Filtering values with Where 4.5. Combining Option and IEnumerable with Bind 4.6. Coding at different levels of abstraction Chapter 5. Designing programs with function composition 5.1. Function composition 5.2. Thinking in terms of data flow 5.3. Programming workflows 5.4. An introduction to functional domain modeling 5.5. An end-to-end server-side workflow Part 2. Becoming functional Chapter 6. Functional error handling 6.1. A safer way to represent outcomes 6.2. Chaining operations that may fail 6.3. Validation: a perfect use case for Either 6.4. Representing outcomes to client applications 6.5. Variations on the Either theme Chapter 7. Structuring an application with functions 7.1. Partial application: supplying arguments piecemeal 7.2. Overcoming the quirks of method resolution 7.3. Curried functions: optimized for partial application 7.4. Creating a partial-application-friendly API 7.5. Modularizing and composing an application 7.6. Reducing a list to a single value Chapter 8. Working effectively with multi-argument functions 8.1. Function application in the elevated world 8.2. Functors, applicatives, monads 8.3. The monad laws 8.4. Improving readability by using LINQ with any monad 8.5. When to use Bind vs. Apply Chapter 9. Thinking about data functionally 9.1. The pitfalls of state mutation 9.2. Understanding state, identity, and change 9.3. Enforcing immutability 9.4. A short introduction to functional data structures Chapter 10. Event sourcing: a functional approach to persistence 10.1. Thinking functionally about data storage 10.2. Event sourcing basics 10.3. Architecture of an event-sourced system 10.4. Comparing different approaches to immutable storage Part 3. Advanced techniques Chapter 11. Lazy computations, continuations, and the beauty of monadic composition 11.1. The virtue of laziness 11.2. Exception handling with Try 11.3. Creating a middleware pipeline for DB access Summary Chapter 12. Stateful programs and stateful computations 12.1. Programs that manage state 12.2. A language for generating random data 12.3. A general pattern for stateful computations Summary Chapter 13. Working with asynchronous computations 13.1. Asynchronous computations 13.2. Traversables: working with lists of elevated values 13.3. Combining asynchrony and validation (or any other two monadic effects) Summary Chapter 14. Data streams and the Reactive Extensions 14.1. Representing data streams with IObservable 14.2. Creating IObservables 14.3. Transforming and combining data streams 14.4. Implementing logic that spans multiple events 14.5. When should you use IObservable? Summary Chapter 15. An introduction to message-passing concurrency 15.1. The need for shared mutable state 15.2. Understanding message-passing concurrency 15.3. Functional APIs, agent-based implementations 15.4. Message-passing concurrency in LOB applications Summary Inverted chapter dependency graph Functional programming is a way of thinking about programs that emphasizes functions, while avoiding state mutation. It allows us to write elegant, intention-revealing code, that shines in testability and support for concurrency. C# includes a number of functional features and libraries, enabling us to take advantage of these benefits. Functional Programming in C# teaches you to apply functional thinking to real-world scenarios. You’ll start by learning the principles of functional programming, and how they translate in the C# language. The book then dives into important topics like function composition, data flow, and principles for designing function signatures, types and collections. Through lots of real-world examples, you’ll acquire the tools to tackle programming tasks with a functional approach. The last part of the book deals with advanced topics, including lazy evaluation, stateful computations, asynchrony, and event streams. By the end of this book, you’ll be able to integrate functional techniques, making your C# programs robust and maintainable, and helping you become a more well-rounded developer.