C# - Introduction

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C# is a general-purpose, multi-paradigm programming language developed by Microsoft.

The C# programming language allows you to build many types of applications, like:

• Business applications to capture, analyze, and process data
• Dynamic web applications that can be accessed from a web browser
• Games, both 2D and 3D
• Financial and scientific applications
• Cloud-based applications
• Mobile applications

Printing “Hello, World!” in C#

To print “Hello, World!” in C#, you can use the following code:

Console.WriteLine("Hello, World!");

This code will output Hello, World! to the console.

Diferences between Console.WriteLine and Console.Write

• Console.WriteLine() prints a message to the output console. At the end of the line, it adds a line feed similar to pressing Enter or Return to create a new line.

• To print to the output console, but without adding a line feed at the end, you use the second technique, Console.Write(). So, the next call to Console.Write() prints another message to the same line.

C# is:

• Strongly typed
• Object-oriented
• Case-sensitive Hello != hello
• Quotes-sensitive '' != ""

Literal Values in C#

In C#, you can use literal values to represent fixed values in your code. A literal value is a constant value that never changes. For example:

• 123 is an integer literal = int
• 'a' is a character literal = char
• "Hello, World!" is a string literal = string
• Floating-point literals = float, double, decimal

Float Type    Precision
----------------------------
float         ~6-9 digits e.g. 3.14F
double        ~15-17 digits e.g. 4.14159
decimal        28-29 digits e.g. 5.78349m

Here, precision reflects the number of digits past the decimal that are accurate.

• F is used to denote a float literal.
• m is used to denote a decimal literal.
• double literals are the default floating-point type in C#.

Declaring Variables in C#

To create a new variable, you must first declare the data type of the variable, and then give it a name. For example:

int myNumber;

Variable naming rules and conventions

A software developer once famously said “The hardest part of software development is naming things.”

Not only does the name of a variable have to follow certain syntax rules, it should also be used to make the code more human-readable and understandable.

That’s a lot to ask of one line of code!

Here’s a few important considerations about variable names:

• They can contain alphanumeric characters and the underscore character. Special characters like the hash symbol # (also known as the number symbol or pound symbol) or dollar symbol $ are not allowed.
• They must begin with an alphabetical letter or an underscore, not a number.
• They are case-sensitive, meaning that string Value; and string value; are two different variables.
• They must not be a C# keyword. For example, you cannot use the following variable declarations: decimal decimal; or string string;.

Assigning Values to Variables in C#

• To assign a value to a variable, you use the assignment operator =. For example:

int myNumber;
myNumber = 123;

• You can also declare and assign a value to a variable in a single line.
• For example:

int myNumber = 123;

• This is called variable initialization.

Implicit and Explicit Variable Declaration

• In C#, you can declare a variable using the var keyword.
• This is called an implicit variable declaration.
• For example:

var myNumber = 123;

• The C# compiler will automatically determine the data type of the variable based on the value assigned to it.

• You can also declare a variable using an explicit variable declaration. For example:

int myNumber = 123;

In this case, you explicitly specify the data type of the variable.

Variables using the var keyword must be initialized

• It’s important to understand that the var keyword is dependent on the value you use to initialize the variable.
• If you try to use the var keyword without initializing the variable, you’ll receive an error when you attempt to compile your code.

var myNumber; // Error: Implicitly-typed variables must be initialized