intro-to-dotnet-web-dev/2-csharp

C# Crash Course

In this C# Crash Course, we'll go over the basics of C# so that you'll be ready to build out exciting web apps in emails 3, 4, and 5! We'll start by going through the key attributes of C#, syntax basics, and introduce you to OOP. In each section, we'll link you to some quick in-browser C# challenges so you can apply these concepts.

Topics you'll learn

• Language attributes
• Syntax basics
• Object Oriented Programming

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Language attributes

C# is a strongly typed, compiled, object oriented language. Let's break this down.

Strongly typed

In a strongly typed language, every variable has a defined type. Some of these types include:

• String, "Hello world!"
• Char, 'a'
• int, 3
• decimal, 1.5
• bool, True

Compiler

A compiler converts the code you write into a format that your computer can understand.After you write C# and build it, the C# compiler (called Roslyn) will analyze your code to check for any errors.

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The basics

Here's a piece of code that will print "Hello world!" to the console.

using System;

Console.WriteLine("Hello world!");

Keywords

With C#, you use keywords like using and Console. Keywords are predefined, reserved identifiers that have special meanings to the compiler.

Accessing methods

The Dot in Console.WriteLine allows us to access methods and properties. In this example, Console is a type that represents the console window. WriteLine is a method of the Console type that prints a line of text to that text console.

Parameters

In this example, we use parentheses pass a string as a parameter to Console.WriteLine.

Variables

In C#, variables allow you to temporarily store a value in memory. In C#, you must declare a vaiable before using it.

var cSharp = "really cool";

In this example, we created a string called cSharp. You can use the var keyword to declare local variables without explicitly giving them a type.

Variable names can contain alphanumeric characters and underscores, but no special characters. They also cannot be keywords.

Syntax cheat sheet

Semicolons

Every statement is ended by a semicolon

Console.WriteLine("there is a ';' at the end of this statement");

Comments

You can make comments by using 2 slashes

// this is a comment is C#

Case sensitive

C# is case sensitive! For example, a variable "cat" is completely different from a variable "CAT". csharp var cat = "meow"; var CAT = "rawr";

Arithmetic Operators

These are probably familiar to you!

symbol	what it does
+	addition
-	subtraction
*	multiplication
/	division
%	remainder
++	increment
--	decrement

Boolean expressions

We use booleans to compare two or more things.

symbol	what it does
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal
==	equal
!=	not equal

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Object Oriented Programming

C# is an object-oriented language. Objects are defined by Classes. In other words, an Object is an instance of a class. One way to think about this is that a class is like the blue prints for a house. The actual house that is built is an objects because it is an instance of this blue print.

Properties and methods

Objects inherently have attributes. In C# we call these properties. The attributes of a house may be the number of doors, what color the house is painted, etc.

We can also define methods which describe what an object can do. For example, you can sell your house.

Let's look at an example House class:

// The namespace declaration provides a way to logically organize your classes
namespace Classes;

public class House
{
  // House properties
    public string Address { get; }
    public int Size { get;}

  // House methods
    public void SellHouse(decimal amount, DateTime date)
    {
    }
}

Constructor

We can define a constructor to allow us to create new House objects.

public House(string address, int squareFeet)
{
    this.Address = address;
    this.Size = squareFeet;
}

When we create an object with new this constructor will be called.

using Classes;

// Let's create a 1500 square foot house on Candy Cane Lane
var house = new House("123 Candy Cane Lane", 1500);

Mini Challenges!

Each of these mini challenges is designed so that you can apply C# concepts to mini coding exercises. These challenges are all sourced from Microsoft documentation and will allow you to get coding inside your browser. Easy peasy!

#	Challenge	Solution	Duration	What you will learn	More information
1	Hello World	N/A	3 min	case sensitive, strings, comments	Intro to C# Tutorial, C# documentation
2	Variables	Solution	5 min	variables, data types, strings, ints, decimals	String formatting tutorial, C# documentation
3	Operating on numbers	Solution	2 min	ints, decimals	Number operations tutorial, C# documentation
4	Making clean code	Solution	5 min	topics	C# coding conventions

Bonus and more ways to connect

Want more practice with C#? The .NET team has you covered. Here's a few learning resources:

• C# Video Series on Microsoft Docs or YouTube
• Self Guided Tutorials on Microsoft Learn
• Learn to Code Page

Connect with us! Check out the .NET Community Page to find links to our blogs, YouTube, Twitter, and more.