The first three chapters form Part I, in which there is a detailed discussion of polymorphism and the use of abstract classes and interfaces. Here, code comments will be examined, and you will learn when to use them effectively. These are the fundamental building blocks for the rest of the book.

In the world of programming, there is no shortage of programming principles and design guidelines. Each of these suggestions has its own benefits. To become a professional programmer, you do not need to learn everything at the same time. In Part II, I discuss six design principles, which include the SOLID principles and the DRY principle. These are the foundation of well-known design patterns.

The best way to learn is by doing and analyzing case studies. So, in Part III of the book, you will see interesting applications that use some well-known patterns. This part gives you hints about how a professional coder develops an enterprise application.

Handling errors is an unavoidable part of programming. Particularly, runtime exceptions are dangerous, and often they appear in the form of NullReferenceException in C#. Part IV focuses on them, discusses different case studies with easy-to-understand examples, and provides useful suggestions about possible improvements.

There is no end to learning. So, Part V includes some interesting topics such as how to prevent memory leaks, how to choose between a static method and an instance method, and some common terms from software development that are not discussed in detail in this book. A quick overview of these topics will help your future learnings and experiments.

You can download all the source codes for the book from the publisher’s website. I have a plan to maintain the “errata,” and, if required, I can also make some updates/announcements there. So, I suggest you visit those pages to receive any important corrections or updates.

Are you familiar with basic constructs in C# and object-oriented concepts such as polymorphism, inheritance, abstraction, and encapsulation?

Do you know how to set up your coding environment?

Have you completed at least one introductory course on C# and now are interested in writing better programs?

Are you also interested to know how a professional programmer designs their applications?

Are you absolutely new to C#?

Are you looking for advanced concepts in C#, excluding the topics mentioned previously?

Are you interested in exploring a book where the focus is not on standard design principles?

Do you not like Windows, Visual Studio, and/or .NET and want to learn and use C# without them?

This book works best if you’ve gone through an introductory course on C# and are familiar with the common terms, such as polymorphism, and have heard about abstract classes and interfaces. If this is not the case, please read about these topics before you start reading this book.

I suggest you go through the chapters sequentially. This is because some fundamental design techniques may have been discussed in a previous chapter, and I have not repeated those techniques in later chapters.

I started this book using Microsoft Visual Studio Community 2022 in a Windows 10 environment. This community edition is free of charge. When I started the book, I started with the latest versions of C# that were available at that time. You can easily guess that version updates kept coming, so I kept updating my code repository. When I finished my first draft, I had the most recent version of Visual Studio Community 2022 (version 17.3.3). Almost in every case, my target framework was .NET 7.0, which supports C# 11.

In this context, it is useful to know that nowadays the C# language version is automatically selected based on your project’s target framework(s), so you can always get the highest compatible version by default.

For example, C# 11 is for .NET 7 and later versions. Similarly, C# 10 is supported only on .NET 6 and newer versions. C# 9 is supported only on .NET 5 and newer versions. C# 8.0 is supported only on .NET Core 3.x and newer versions. If you are interested in the C# language versioning, you can go to this link: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/configure-language-version.

The fact is that these version updates will come continuously, but I strongly believe that these version details should not matter much to you because I have used the fundamental constructs of C#. So, the code in this book should execute smoothly in the upcoming versions of C#/Visual Studio as well. Though I also believe that the results should not vary in other environments, you know the nature of software—it is naughty. So, I recommend that if you want to see the exact same output, you mimic the same environment.

If you do not use the Windows operating system, you can use Visual Studio Code, which is also a source-code editor developed by Microsoft to support Windows, Linux, or Mac operating systems. This multiplatform IDE is also free.

You can download and install the Visual Studio IDE from https://visualstudio.microsoft.com/downloads/. You will the screen shown in Figure I-1.

Note At the time of writing, this information is correct. But the link and policies may change in the future.

I have also installed the class designer component in Visual Studio 2022 to draw class diagrams for my programs. They’ll help you understand the code better.