Lessons - C# MasterClass

1. Output & Display Data

In C#, we use the Console class to display text to the user.

// WriteLine prints text and goes to a new line
Console.WriteLine("Hello World!");

// Write prints text on the same line
Console.Write("I am learning ");
Console.Write("C#");

2. Input Data

To get data from the user, use Console.ReadLine(). Remember, it always returns a String.

Console.Write("Enter your name: ");
string name = Console.ReadLine();
Console.WriteLine("Welcome " + name);

// Converting String to Integer
Console.Write("Enter your age: ");
int age = Convert.ToInt32(Console.ReadLine());

3. Basic Numeric Operators

Standard math operators in C#:

Operator	Meaning	Example
+	Add	x + y
-	Subtract	x - y
*	Multiply	x * y
/	Divide	x / y
%	Modulus	x % y

4. Conditions (If / Else)

Use if statements to specify a block of code to be executed if a condition is true.

[Image of flowchart of if else statement]

int time = 20;
if (time < 18) 
{
  Console.WriteLine("Good day.");
} 
else 
{
  Console.WriteLine("Good evening.");
}

5. Loops (Iteration)

Loops can execute a block of code as long as a specified condition is reached.

For Loop

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

While Loop

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

6. Arrays

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.

// Declare an array of strings
string[] cars = {"Volvo", "BMW", "Ford", "Mazda"};

// Access the first element (Index starts at 0)
Console.WriteLine(cars[0]); // Outputs: Volvo

// Change an element
cars[0] = "Opel";

7. Switch Statement

Use the switch statement to select one of many code blocks to be executed. It's cleaner than many if..else statements.

int day = 4;
switch (day) 
{
  case 1:
    Console.WriteLine("Monday");
    break;
  case 2:
    Console.WriteLine("Tuesday");
    break;
  default:
    Console.WriteLine("Other day");
    break;
}

8. Methods

A method is a block of code which only runs when it is called. You can pass data, known as parameters, into a method.

class Program
{
  // Define the method
  static void MyMethod(string fname) 
  {
    Console.WriteLine(fname + " is a student");
  }

  static void Main(string[] args)
  {
    // Call the method
    MyMethod("Mahmoud");
    MyMethod("Ahmed");
  }
}