1ST EDITION Real-World Implementation of C R # e C# Design Patt erns a D l - e W s i o g r n l d As a software developer, you need to learn new languages and simultaneously get familiarized with the P a I programming paradigms and methods of leveraging patt erns, as both a communications tool and an m tt advantage when designing well-writt en, easy-to-maintain code. Design patt erns, being a collection of best p e practices, provide the necessary wisdom to help you overcome common sets of challenges in object-oriented l r e design and programming. n m 1ST EDITION s This practical guide to design patt erns helps C# developers put their programming knowledge to work. The e book takes a hands-on approach to introducing patt erns and anti-patt erns, elaborating on 14 patt erns along n t with their real-world implementations. Throughout the book, you’ll understand the implementation of each a patt ern, as well as fi nd out how to successfully implement those patt erns in C# code within the context of a t i Real-World real-world project. o n By the end of this design patt erns book, you’ll be able to recognize situations that tempt you to reinvent the o wheel, and quickly avoid the time and cost associated with solving common and well-understood problems f with batt le-tested design patt erns. Implementation of WHAT YOU WILL LEARN B C# Design Patt erns R • Get to grips with patterns, and discover how to conceive and document them U C • Explore common patterns that may come up in your everyday work E • Recognize common anti-patterns early in the process M . • Use creational patterns to create flexible and robust object structures • Enhance class designs with structural patterns V Overcome daily programming challenges using A • Simplify object interaction and behavior with behavioral patterns N elements of reusable object-oriented software H O R N I BRUCE M. VAN HORN II I Foreword by Van Symons, CTO Visual Storage Intelligence Re a l -Wo r l d I m p l e m e n t a t i o n o f C # D e s i g n Pa t te r n s Real-World Implementation of C# Design Patterns Overcome daily programming challenges using elements of reusable object-oriented software Bruce M. Van Horn II BIRMINGHAM—MUMBAI Real-World Implementation of C# Design Patterns Copyright © 2022 Packt Publishing All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews. Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing or its dealers and distributors, will be held liable for any damages caused or alleged to have been caused directly or indirectly by this book. Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information. Group Product Manager: Gebin George Publishing Product Manager: Gebin George Senior Editor: Kinnari Chohan Technical Editor: Jubit Pincy Copy Editor: Safis Editing Project Coordinator: Manisha Singh Proofreader: Safis Editing Indexer: Subalakshmi Govindhan Production Designer: Roshan Kawale Marketing Coordinator: Sonakshi Bubbar First published: September 2022 Production reference: 1270922 Published by Packt Publishing Ltd. Livery Place 35 Livery Street Birmingham B3 2PB, UK. ISBN 978-1-80324-273-6 www.packt.com For my beautiful wife Karina, and my children Kitty and Phoebe, who helped me truly understand Ruth 1:16. In memory and gratitude to my mother and father, who paid for my first three computers, back when normal people didn’t own them. In memory of Dr. Charles Gettys for motivating me by telling me I would probably fail, and then teaching me everything he knew about computers. For Van Symons, who saw past my wheelchair and gambled on me when nobody else would, and who gave me a place and the opportunity to do the best work of my career. For my students at Southern Methodist University and Richland College, from whom I’ve learned as much as I’ve taught. For my work family at Clear Technologies/Visual Storage Intelligence. In memory of my student, Tom, who really could type ActionScript code with his feet. These are the people who inspire me and for whom I am deeply grateful. Above all, I am thankful to my Lord and Savior Jesus Christ who makes all things possible (Philippians 4:13), along with His Father who invented all the electrons and silicon, without which none of this computer stuff would exist (Genesis 1:14–19). Fo r e wo r d I have known and worked with Bruce M. Van Horn II for the past 10 years. Bruce has been the lead software developer for Visual Storage Intelligence, an analytical software technology for analyzing infrastructure hardware and software to ensure the optimum use of on-premises and cloud resources is maximized. Bruce is a leader in creating and leveraging innovative software technologies to meet demanding customer needs in a fast-paced IT environment. In this book, Bruce teaches you how to leverage software engineering techniques known as design patterns to solve real-world problems in an efficient and effective manner. Using patterns will help you solve problems effectively without reinventing the wheel. It will also keep your code healthy and stable. Learning patterns are a must-have requirement in the career of any software engineer that we’ve hired at our start-ups. There is no question as to whether you should learn patterns; the question is really, where can you find a resource that teaches patterns in a way that is easy to understand and apply? There are many books on patterns in the marketplace but most have a very academic focus. This book is very different and somewhat unique. Instead of a dry treatment that reads like a doctoral thesis, Bruce presents you with the story of two sisters who form a tech start-up. Problems are encountered, requirements change, and at one point, so does the direction of the business. These are all normal and frequent occurrences, and the software that runs the company must be able to adapt. Most books cover development topics in a vacuum. All the designs are perfect, and the code always runs on the first try. That isn’t real life. The story in this book follows a more realistic arc. The characters get into jams and use patterns to get out of them. Oftentimes, knowing when, where, and how to make use of these patterns can be critical to business success, and that’s what you’re going to learn in this book. Bruce is not only a brilliant software engineer but also one of the best technology educators I have met in my 45-year career. He has the unique ability to not only understand the technology but also understand both the best places to make use of it, and also the places where specific technologies are not appropriate for the issues being analyzed. Bruce shows you how to leverage the most important Gang of Four patterns in simple-to-understand examples, as well as how to use the patterns to solve problems in your daily work. Reading this book made software design patterns come to life and helped me understand how to leverage patterns in a real-world business context. Van Symons CTO Visual Storage Intelligence Co n t r i b u t o r s About the author Bruce M. Van Horn II is an architect and lead developer for Clear Technology’s Visual Storage Intelligence SaaS product. He has over 30 years’ experience writing software and over 25 years’ experience teaching software development at a university level. He currently teaches full stack software development at Southern Methodist University’s code boot camp. He is a Certified ScrumMaster (CSM). Ten years ago, he was diagnosed with dermatomyositis and was told he would never walk, speak, or eat nachos again. Through faith and hard work, he beat the odds and today enjoys riding bicycles with his daughters, Katherine (Kitty) and Phoebe. He eats nachos regularly with Karina, the love of his life. About the reviewers Alexej Sommer is a professional .NET developer with expertise in a variety of technologies, including ASP.NET Core, WPF, UWP, Xamarin, and Azure. He is also MCP/MCSD- and Azure-certified. He’s a winner of Microsoft’s Most Valuable Professional 2016–2019 in the Windows Development category. At present, he sometimes participates in conferences as a speaker. Sarita Nag was born in India and she earned her master's degree in computer science from KIIT University, Bhubaneswar, Orissa. Sarita began her career as Software Engineer from Thomson Reuters and since then, she worked on many multinational companies and is currently working at FISERV. She is an experienced software engineer with passion for developing innovative programs that expedite the efficiency and effectiveness of organizational success. Well-versed in technology and writing code to create systems that are reliable and user-friendly. She has 10+ years of experience in various phases of Software Development Life cycle (SDLC) and Agile methodologies such as Analysis, Design, Development, Testing, Deployment, and Maintenance in various domains like Tax and accounting, Financial, Communication Media, and Customer relationship. Table of Contents Preface xv Part 1: Introduction to Patterns (Pasta) and Antipatterns (Antipasta) 1 There's a Big Ball of Mud on Your Plate of Spaghetti 3 Technical requirements 6 Complexity 12 No battle plan survives first Change 12 contact with the enemy 7 Scale 12 The Stovepipe system 7 The Golden Hammer 12 The Big Ball of Mud 9 A throwaway code example 15 Time 11 How can patterns help? 29 Cost 11 Summary 31 Experience 11 Questions 32 Skill 11 Further reading 32 Visibility 12 2 Prepping for Practical Real-World Applications of Patterns in C# 33 Becoming a prepper 33 Spaghetti code 35 Technical requirements 34 Lasagna code 36 Ravioli – the ultimate in pasta code 40 Spaghetti < lasagna < ravioli – software evolution explained The foundational principle – writing with pasta 35 clean code 41