In One Video

Lesson 32
Author : GOUP
Last Updated : September, 2020

C# Overview

C# (C Sharp) is a general purpose, staticly typed, object oriented programming language that was founded in 2000 by Microsoft as part of their .NET Initiative.

C# was designed to be portable and fast and is tightly coupled with Microsoft’s .Net Framework. It was created along side the .Net framework in the late 90s.

C# is one of the most popular programming languages in the world, and can be used to write applications on almost every platform including, Windows, Mac, iOS, Android, and Linux.

In fact more and more people are using C# to write cross platform apps everyday because it allows for a shared codebase across platforms. Basically you could write all of your backend business logic and database management code once, and use it on iphone, android and desktop.

How C# Runs

All C# code is compiled down into an intermediate language called common language which is then translated and executed by the .Net runtime also called the Common Language Runtime (CLR). This ensures that C# programs can be run on virtually any combination of hardware and operating system.

The underlying C# runtime uses an automatic garbage collector to manage memory, and the syntax of C# is largly influenced by Java.

Choosing an IDE

Most developers choose to write C# using a specilized integrated development enviornment called Visual Studio. Visual Studio is an IDE that is maintained and developed by Microsoft, so it’s the best choice and realisticly the only choice for writing C# applications.

Code

Printing

CopyConsole.WriteLine("Hello");
Console.Write("World");
Console.WriteLine("!");

Variables and Data Types

Copy/*
Names are case-sensitive and may begin with:
     letters, _, @
After, may include
     letters, numbers, _
Convention says
     Start with a lowercase word, then additional words are capitalized
     ex. myFirstVariable
*/
string name = "Mike";    // String's are objects not primitives
char testGrade = 'A';    // single 16-bit Unicode character.

// short, int, long can be pre-pended with 'u' for 'unsigned'
byte age0 = 0;           // 8-bit unsigned integer
short age1 = 10;         // 16-bit signed integer.
int age2 = 20;           // 32-bit signed integer
long age3 = 30L;         // 64-bit signed integer

float gpa0 = 2.5F;       // 32-bit floating point
double gpa1 = 3.5;       // 64-bit double-precision floating point
decimal gpa2 = 4.5M;     // 128-bit precise decimal

bool isTall;             // 1 bit -> true/false
isTall = true;

name = "John";

Console.WriteLine("Your name is " + name);
Console.WriteLine($"Your name is {name}");

Casting and Converting

CopyConsole.WriteLine( (int)3.14 );
Console.WriteLine( (double)3 );

int intFromString = Convert.ToInt32("50");
double doubleFromString = Convert.ToDouble("50.99");

Console.WriteLine(100 + intFromString);
Console.WriteLine( 100 + doubleFromString );

Strings

Copystring greeting = "Hello";
//      indexes:   01234

Console.WriteLine( greeting.Length );
Console.WriteLine( greeting[0] );
Console.WriteLine( greeting.IndexOf("llo") );
Console.WriteLine( greeting.IndexOf("z") );
Console.WriteLine( greeting.Substring(2) );
Console.WriteLine( greeting.Substring(1, 3) );

Numbers

CopyConsole.WriteLine(2 * 3);      // Basic Arithmetic: +, -, /, *
Console.WriteLine(10 % 3);      // Modulus Op. : returns remainder of 10/3
Console.WriteLine(1 + 2 * 3);   // order of operations
Console.WriteLine(10 / 3.0);      // int's and doubles


int num = 10;
num += 100; // +=, -=, /=, *=
Console.WriteLine(num);

num++;
Console.WriteLine(num);

Console.WriteLine( Math.Pow(2, 3) );
Console.WriteLine( Math.Sqrt(144) );
Console.WriteLine( Math.Round(2.7) );

User Input

CopyConsole.Write("Enter username: ");
string username = Console.ReadLine();
Console.WriteLine($"Hello {username}");

Arrays

Copy//int [] luckyNumbers = new int[10];
int[] luckyNumbers = { 4, 8, 15, 16, 23, 42 };
//         indexes:    0  1  2   3   4   5
luckyNumbers[0] = 90;
Console.WriteLine(luckyNumbers[0]);
Console.WriteLine(luckyNumbers[1]);
Console.WriteLine(luckyNumbers.Length);

2 Dimensional Arrays

Copy// int [][] numberGrid = new int[2][3];
int[][] numberGrid = { new int[]{ 1, 2 }, new int[]{ 3, 4 } };
numberGrid[0][1] = 99;

Console.WriteLine(numberGrid[0][0]);
Console.WriteLine(numberGrid[0][1]);

ArrayList

CopyArrayList friends = new ArrayList();
friends.Add("Oscar");
friends.Add("Angela");
friends.Add("Kevin");

//friends.Remove("Oscar");
Console.WriteLine(friends[0]);
Console.WriteLine(friends[1]);
Console.WriteLine(friends.Contains("Oscar"));
Console.WriteLine(friends.Count);

Methods

Copypublic static void Main(string [] args){
     int sum = AddNumbers(4, 60);
     Console.WriteLine(sum);
}

public static int AddNumbers(int num1, int num2){
     return num1 + num2;
}

If Statements

Copybool isStudent = false;
bool isSmart = false;

if (isStudent && isSmart)
{
   Console.WriteLine("You are a student");
}
else if (isStudent && !isSmart)
{
   Console.WriteLine("You are not a smart student");
}
else
{
   Console.WriteLine("You are not a student and not smart");
}

// >, <, >=, <=, !=, ==
if (1 < 3)
{
   Console.WriteLine("number omparison was true");
}

Switch Statements

Copychar myGrade = 'A';
switch(myGrade){
     case 'A':
          Console.WriteLine("You Pass");
          break;
     case 'F':
          Console.WriteLine("You fail");
          break;
     default:
          Console.WriteLine("Invalid grade");
}

While Loops

Copyint index = 1;
while(index <= 5){
     Console.WriteLine(index);
     index++;
}

do{
   Console.WriteLine(index);
   index++;
}while(index <= 5);

For Loops

Copyfor(int i = 0; i < 5; i++){
     Console.WriteLine(i);
}

int[] luckyNums = {4, 8, 15, 16, 23, 42};
foreach(int luckyNum in luckyNums){
     Console.WriteLine(luckyNum);
}

Exception Catching

Copytry{
  int division = 10 / Convert.ToInt32(Console.ReadLine());
}catch(DivideByZeroException e){
     Console.WriteLine(e);
}catch(Exception e){
     Console.WriteLine(e);
     // Not best practice to use general Exception
}

throw new DivideByZeroException("can't add numbers");

Classes and Objects

Copypublic class Book{
     public string title;
     public string author;
     public static string staticAttribute = "My Static Attribute";

     public void ReadBook(){
       Console.WriteLine($"Reading {this.title} by {this.author}");
     }
}

Book book1 = new Book();
book1.title = "Harry Potter";
book1.author = "JK Rowling";

book1.ReadBook();
Console.WriteLine(book1.title);

Book book2 = new Book();
book2.title = "Lord of the Rings";
book2.author = "JRR Tolkien";

book2.ReadBook();
Console.WriteLine(book2.title);
Console.WriteLine(Book.staticAttribute);

Constructors

Copypublic class Book{
     public String title;
     public String author;

     public Book(String title, String author){
          this.title = title;
          this.author = author;
     }

     public void readBook(){
          Console.WriteLine("Reading " + this.title + " by " + this.author);
     }
}

Book book1 = new Book("Harry Potter", "JK Rowling");
Console.WriteLine(book1.title);

Book book2 = new Book("Lord of the Rings", "JRR Tolkien");
Console.WriteLine(book2.title);

Getters and Setters

Copypublic class Book{
     private String title;
     private String author;

     public Book(String title, String author){
          this.setTitle(title);
          this.setAuthor(author);
     }

     public String getTitle(){
          return this.title;
     }
     public void setTitle(String title){
          this.title = title;
     }

     public String getAuthor(){
          return this.author;
     }
     public void setAuthor(String author){
          this.author = author;
     }
}

Book book1 = new Book("Harry Potter", "JK Rowling");
Console.WriteLine(book1.getTitle());

Book book2 = new Book("Lord of the Rings", "JRR Tolkien");
Console.WriteLine(book2.getTitle());

Inheritance

Copypublic class Chef
{

   public String name;
   public int age;

   public Chef(String name, int age)
   {
       this.name = name;
       this.age = age;
   }

   public void MakeChicken()
   {
       Console.WriteLine("The chef makes chicken");
   }

   public void MakeSalad()
   {
       Console.WriteLine("The chef makes salad");
   }

   public virtual void MakeSpecialDish()
   {
       Console.WriteLine("The chef makes a special dish");
   }
}
public class ItalianChef : Chef
{

   public String countryOfOrigin;

   public ItalianChef(String name, int age, String countryOfOrigin)
     : base(name, age)
   {
       this.countryOfOrigin = countryOfOrigin;
   }

   public void MakePasta()
   {
       Console.WriteLine("The Chef make's past");
   }
   public override void MakeSpecialDish()
   {
       Console.WriteLine("The chef makes chicken parm");
   }
}

Chef myChef = new Chef("Gordon Ramsay", 50);
myChef.MakeChicken();

ItalianChef myItalianChef = new ItalianChef("Massimo Bottura", 55, "Italy");
myItalianChef.MakeChicken();
Console.WriteLine(myItalianChef.countryOfOrigin);

Abstract Classes and Methods

Copyabstract class Vehicle
{
   public abstract void move();
   public void getDescription()
   {
       Console.WriteLine("Vehicles are used for transportation");
   }
}

class Bicycle : Vehicle
{
   public override void move()
   {
       Console.WriteLine("The bicycle pedals forward");
   }
}

class Plane : Vehicle
{
   public override void move()
   {
       Console.WriteLine("The plane flys through the sky");
   }
}

Interface Inheritance

Copypublic interface Animal
{
  void Speak();
  void Eat();
}
public class Dog : Animal
{
  public void Speak()
  {
       Console.WriteLine("Woof Woof");
  }
}
public class Cat : Animal
{
  public void Speak()
  {
       Console.WriteLine("Meow Meow");
  }
}

Animal[] animals = {
     new Dog(),
     new Cat()
};
foreach(Animal animal in animals){
     animal.speak();
}