C# Cheat Sheet

Core C# syntax, LINQ queries, generic collections, async/await patterns, and object-oriented features for building .NET applications.

2 PagesIntermediateApr 8, 2026

Basic Syntax

Variables, control flow, and console output.

csharp

using System;class Program {    static void Main(string[] args) {        int age = 30;        string name = "Ada";        double pi = 3.14159;        bool isFun = true;        if (age >= 18) {            Console.WriteLine($"{name} is an adult");        }        for (int i = 0; i < 5; i++) {            Console.WriteLine($"Count: {i}");        }    }}

LINQ

Query and transform collections declaratively.

csharp

var nums = new List<int> { 5, 3, 1, 4, 2 };var evens = nums.Where(n => n % 2 == 0)                 .Select(n => n * n)                 .ToList();          // [16, 4]var sorted = nums.OrderBy(n => n).ToList();  // [1, 2, 3, 4, 5]int sum = nums.Sum();                         // 15var first = nums.FirstOrDefault(n => n > 3);  // 5

Async/Await

Non-blocking asynchronous operations.

csharp

using System.Net.Http;using System.Threading.Tasks;async Task<string> FetchDataAsync(string url) {    using var client = new HttpClient();    string result = await client.GetStringAsync(url);    return result;}async Task Main() {    string data = await FetchDataAsync("https://api.example.com");    Console.WriteLine(data);}