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.
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.
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.
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.
```csharp
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
1. Every statement is ended by a semicolon
```csharp
Console.WriteLine("there is a ';' at the end of this statement");
```
1. You can make comments by using 2 slashes
```csharp
// this is a comment is C#
```
1. C# is case sensitive! For example, a variable "cat" is completely different from a variable "CAT".
```csharp
var cat = "meow";
var CAT = "rawr";
```
1. Arithmetic operators
These are probably familiar to you!
| symbol | what it does |
| --- | ------ |
| + | addition |
| - | subtraction |
| * | multiplication |
| / | division |
| % | remainder |
| ++ | increment |
| -- | decrement |
2. 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 |
---
# OOP
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.
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:
```csharp
// 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)
{
}
}
```
We can define a **constructor** to allow us to create new House objects.
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!
Want more practice with C#? The .NET team has you covered. Here's a few learning resources:
* C# Video Series on [Microsoft Docs](https://docs.microsoft.com/shows/CSharp-101/?WT.mc_id=dotnet-35129-website) or [YouTube](https://www.youtube.com/watch?v=Z5JS36NlJiU)
* Self Guided Tutorials on [Microsoft Learn](https://docs.microsoft.com/users/dotnet/collections/yz26f8y64n7k07)
* [Learn to Code Page](https://dotnet.microsoft.com/learntocode)
Connect with us! Check out the [.NET Community Page](https://dotnet.microsoft.com/platform/community) to find links to our blogs, YouTube, Twitter, and more.
