This part of the book is about the C# language—the grammar and vocabulary that you will use every day to write the source code for your applications.

Programming languages have many similarities to human languages, except that in programming languages, you can make up your own words, just like Dr. Seuss!

In a book written by Dr. Seuss in 1950, If I Ran the Zoo, he states this:

"And then, just to show them, I'll sail to Ka-Troo And Bring Back an It-Kutch, a Preep, and a Proo, A Nerkle, a Nerd, and a Seersucker, too!"

Understanding language versions and features

This part of the book covers the C# programming language and is written primarily for beginners, so it covers the fundamental topics that all developers need to know, from declaring variables to storing data to how to define your own custom data types.

Advanced and obscure topics like ref local variable reassignment and reference semantics with value types are not covered...

To learn C#, you will need to create some simple applications. To avoid overloading you with too much information too soon, the chapters in the first part of this book will use the simplest type of application: a console application.

Let's start by looking at the basics of the grammar and vocabulary of C#. Throughout this chapter, you will create multiple console applications, with each one showing a feature of the C# language.

1. If you've completed Chapter 1, Hello, C#! Welcome, .NET!, then you will already have a Code folder in your user folder. If not, then you'll need to create it.
2. Create a subfolder named Chapter02, with a sub-subfolder named Basics.
3. Start Visual Studio Code and open the Chapter02/Basics folder.
4. In Visual Studio Code, navigate to View | Terminal, and enter the following command:

   dotnet new console

5. In EXPLORER, click the Program.cs file, and then click on Yes to add the missing required assets...

All applications process data. Data comes in, data is processed, and then data goes out. Data usually comes into our program from files, databases, or user input, and it can be put temporarily into variables that will be stored in the memory of the running program. When the program ends, the data in memory is lost. Data is usually output to files and databases, or to the screen or a printer. When using variables, you should think about, firstly, how much space it takes in the memory, and, secondly, how fast it can be processed.

We control this by picking an appropriate type. You can think of simple common types such as int and double as being different-sized storage boxes, where a smaller box would take less memory but may not be as fast at being processed; for example, adding 16-bit numbers might not be processed as fast as adding 64-bit numbers on a 64-bit operating system. Some of these boxes may be stacked close by, and some may be thrown into a big...

You have now seen how to store primitive values like numbers in variables. But what if a variable does not yet have a value? How can we indicate that? C# has the concept of a null value, which can be used to indicate that a variable has not been set.

Making a value type nullable

By default, value types like int and DateTime must always have a value, hence their name. Sometimes, for example, when reading values stored in a database that allows empty, missing, or null values, it is convenient to allow a value type to be null, we call this a nullable value type.

You can enable this by adding a question mark as a suffix to the type when declaring a variable. Let's see an example.

1. In the Chapter02 folder, create a new folder named NullHandling.
2. Add the NullHandling folder to the Chapter02 workspace.
3. Create a new Terminal window for the NullHandling project.
4. Create a new console application project in the NullHandling folder.
...

We have already created and used basic console applications, but we're now at a stage where we should delve into them more deeply.

Console applications are text-based and are run at the command line. They typically perform simple tasks that need to be scripted, such as compiling a file or encrypting a section of a configuration file.

Equally they can also have arguments passed to them to control their behavior. An example of this would be to create a new console app using the F# language with a specified name instead of using the name of the current folder, as shown in the following command line:

dotnet new console -lang "F#" -name "ExploringConsole"

Displaying output to the user

The two most common tasks that a console application performs are writing and reading data. We have already been using the WriteLine method to output, but if we didn't want a carriage return at the end of the lines, we could...

Test your knowledge and understanding by answering some questions, get some hands-on practice, and explore the topics covered in this chapter with deeper research.

Exercise 2.1 – Test your knowledge

To get the best answer to some of these questions you will need to do your own research. I want you to "think outside the book" so I have deliberately not provided all the answers in the book.

I want to encourage you to get in the good habit of looking for help elsewhere, following the principle of "teach a person to fish."

What type would you choose for the following "numbers"?

1. A person's telephone number.
2. A person's height.
3. A person's age.
4. A person's salary.
5. A book's ISBN.
6. A book's price.
7. A book's shipping weight.
8. A country's population.
9. The number of stars in the universe.

10. The number of employees in each of the small...

In this chapter, you learned how to declare variables with a specified or an inferred type; we discussed some of the built-in types for numbers, text, and Booleans; we covered how to choose between number types; we covered nullability of types; we learned how to control the output formatting in console apps.

In the next chapter, you will learn about operators, branching, looping, and converting between types.