C# Cheat Sheet — Complete Syntax, OOP Concepts, and Examples

C# Cheat Sheet — Quick Reference Guide for Developers

C# (C-Sharp) is a modern, object-oriented programming language developed by Microsoft. It runs on the .NET framework and is widely used for building desktop apps, web apps, games, and enterprise software.

This C# Cheatsheet gives you a quick and complete overview of all major topics — from basic syntax to advanced OOP and LINQ — with easy-to-understand examples for practical learning.

C# Basics for Beginners

Example:

using System;

namespace HelloWorld {
    class Program {
        static void Main() {
            Console.WriteLine("Hello, C#!");
        }
    }
}

Data Types in C#

C# Variables and Constants

int x = 10;
const double PI = 3.1416;
var message = "Hello!";

• var allows type inference at compile time.
• const defines immutable values.

Operators in C#

Conditional Statements in C#

if (x > 0)
    Console.WriteLine("Positive");
else if (x < 0)
    Console.WriteLine("Negative");
else
    Console.WriteLine("Zero");

Switch Example:

switch (day) {
    case 1: Console.WriteLine("Monday"); break;
    default: Console.WriteLine("Invalid"); break;
}

Loops in C#

Example:

foreach (int n in new int[]{1,2,3})
    Console.WriteLine(n);

C# Functions (Methods)

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

• Static Methods: Belong to the class, not instance.
• Overloading: Same name, different parameters.
• Default Parameters: void Greet(string name="User").

C# Object-Oriented Programming (OOP)

Example:

class Animal {
    public virtual void Speak() {
        Console.WriteLine("Animal sound");
    }
}

class Dog : Animal {
    public override void Speak() {
        Console.WriteLine("Bark");
    }
}

C# Collections

c# cheatsheet, c# programming tutorial, c# syntax guide, c# interview questions, c# oops concepts, c# examples for beginners, c# operators, c# loops examples, c# collections, c# reference pdf

LINQ (Language Integrated Query)

LINQ simplifies querying data in collections.

int[] numbers = { 1, 2, 3, 4, 5 };
var even = from n in numbers where n % 2 == 0 select n;

foreach(var n in even)
    Console.WriteLine(n);

File Handling in C#

using System.IO;

File.WriteAllText("file.txt", "Hello C#");
string content = File.ReadAllText("file.txt");
Console.WriteLine(content);

Exception Handling in C#

try {
    int x = 0;
    int y = 10 / x;
}
catch (DivideByZeroException e) {
    Console.WriteLine(e.Message);
}
finally {
    Console.WriteLine("Cleanup code");
}

Asynchronous Programming in C#

async Task FetchData() {
    await Task.Delay(1000);
    Console.WriteLine("Data loaded");
}

C# Keywords Summary Table

FAQ — C# Programming

Q1: Is C# only used for Windows applications?
No, modern .NET Core allows C# apps to run on Windows, Linux, and macOS.

Q2: What is the difference between C++ and C#?
C++ is a compiled system-level language, while C# runs on the .NET runtime and is designed for managed, high-level development.

Q3: Can I use C# for game development?
Yes, Unity Engine uses C# for all its game scripts.

Q4: Is C# easy to learn for beginners?
Yes! Its syntax is clean, modern, and similar to C, Java, and JavaScript.

Q5: Where can I practice C# online?
Try the PHPOnline C# Compiler for running C# code instantly.