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title: 1. Introduction to C# and .NET
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# Introduction to C# and .NET

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## Overview

* C#
* .NET
* Common Language Infrastructure (CLI)
* Base Class Library (BCL)

## C#

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* The C# (pronounced *c sharp*) programming language was introduced by Microsoft in 2000, alongside the .NET framework
* Unlike C and C++, C# runs on a virtual machine like Java
* Easy to understand, general purpose, high-level, object oriented
* Resembles Java, which was very popular in the 90s
* Newest version is 13.0 from 2024

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![w:600](imgs/1%20Introduction%20to%20C%23%20and%20NET_2.png)

Source:  [http://pypl.github.io/PYPL.html](http://pypl.github.io/PYPL.html)

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## C# Syntax example

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```c#
using System;

namespace MyAwesomeProgram
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}
```

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* Everything is inside a `class`
* Rows = statements
* Curly braces `{` and `}` mark the start and the end of different ***bodies*** of statements
* Semicolon `;` at the end of some statements
* When to use semicolon? Don't worry: Visual Studio will tell you

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* Try out the [online compiler](https://www.programiz.com/csharp-programming/online-compiler/)!

## .NET

* .NET (pronounced *dot net*) is Microsoft's software framework for building and running web services
  * [.NET fundamentals](https://learn.microsoft.com/en-us/dotnet/fundamentals/), [Introduction to .NET](https://learn.microsoft.com/en-us/dotnet/core/introduction)
* Fully supports C#, F# and Visual Basic
* Implements Common Language Infrastructure, so it can compile managed code (languages above) into machine code
* Provides [automatic memory management](https://learn.microsoft.com/en-us/dotnet/standard/automatic-memory-management) via a garbage collector (GC)
* Type-safe and memory-safe thanks to GC and strict compilers

## .NET vs .NET Framework

* *.NET Framework*
  * Launched in 2001
  * Closed-source
  * Windows-only
  * Current version 4.8.1 launched in 2022
* *.NET* (originally *.NET core*)
  * Launched in 2016, Successor to .NET Framework
  * [Open source]([https://github.com/dotnet/](https://github.com/dotnet/))
  * Cross-platform (Linux, Mac, Windows)
  * Current version 9.0 launched in 2024
* We will be using .NET Core as the .NET Framework is considered legacy

## Common Language Infrastructure (CLI)

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* Common Language Infrastructure (CLI) is a standardized specification that decribes how different high-level langauges (like C#) can be run on different platforms without having to be rewritten
* both versions of .NET are ***implementations*** of the CLI
* Another implementation is the free and open-source [Mono](https://www.mono-project.com/) project
  * Used by the Unity game engine and the MonoGame framework 

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![](https://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Overview_of_the_Common_Language_Infrastructure_2015.svg/800px-Overview_of_the_Common_Language_Infrastructure_2015.svg.png)

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## Base Class Library (BCL)

* [Base Class Library](https://learn.microsoft.com/en-us/dotnet/standard/class-library-overview) (BCL) is a set of libraries that every .NET implementation uses, mostly under the `System` namespace
* Consists of common tools like classes and value types that you will need to create your programs
* No need to reinvent the wheel with every new project
  ```csharp
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  ```

## Assignments
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[Assignments about this topic can be found here](https://gitea.buutti.com/education/academy-assignments/src/branch/master/C%23%20Basics/1.%20C%23%20Basics%20Assignments)