Fundamentals of C# Programming

C# is a versatile programming language with a clear, structured syntax. This guide covers essential concepts including program structure, variables, control flow, and methods—the building blocks for creating functional C# applications.

Basic Program Structure

Every C# program requires:

• A class definition (the blueprint for your code)
• A Main method (the entry point where execution begins)

Example: “Hello, World!” Program

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

• Console.WriteLine() prints text to the console.

Variables and Data Types

Variables store data and must be declared with a type.

Common Data Types

Type	Example	Description
int	int age = 25;	Whole numbers
string	string name = “John”;	Text
double	double price = 9.99;	Decimal numbers
bool	bool isActive = true;	True/False values

Type Inference with var

The compiler can automatically detect the type:

var count = 10;  // Compiler infers `int`  
var message = "Hello";  // Infers `string`  

Control Structures

Control structures dictate how code executes based on conditions or loops.

1. If-Else Statements

if (age >= 18)  
{
    Console.WriteLine("You're an adult.");  
}
else  
{
    Console.WriteLine("You're a minor.");  
}

2. Loops

For Loop

for (int i = 0; i < 5; i++)  
{
    Console.WriteLine(i);  // Prints 0 to 4  
}

While Loop

int counter = 0;  
while (counter < 3)  
{
    Console.WriteLine(counter);  
    counter++;  
}

Methods (Functions)

Methods encapsulate reusable logic.

Defining a Method

public static int Add(int a, int b)  
{
    return a + b;  
}

Calling a Method

int result = Add(5, 10);  
Console.WriteLine(result);  // Output: 15  

Practical Example: Simple Calculator

class Calculator  
{
    static void Main(string[] args)  
    {
        Console.WriteLine("Enter first number:");  
        int num1 = int.Parse(Console.ReadLine());  

        Console.WriteLine("Enter second number:");  
        int num2 = int.Parse(Console.ReadLine());  

        int sum = Add(num1, num2);  
        Console.WriteLine($"Sum: {sum}");  
    }

    public static int Add(int a, int b)  
    {
        return a + b;  
    }
}

Handling User Input

Use Console.ReadLine() to capture user input:

Console.WriteLine("What's your name?");  
string userName = Console.ReadLine();  
Console.WriteLine($"Hello, {userName}!");  

Conclusion

Mastering these fundamentals—program structure, variables, control flow, and methods—enables you to build basic C# applications like calculators, interactive prompts, and more. These concepts serve as the foundation for advancing into more complex C# programming.

Next Steps:

• Explore arrays and collections
• Learn about object-oriented programming (OOP)
• Experiment with file I/O and error handling