C# Cheat Sheet

Learn C# from the basics →

Variables & Types

int x = 5; double d = 3.14; bool b = true; char c = 'A';: Basic types
string name = "Ada";: String type
const int Max = 100;: Compile-time constant
var count = 10;: Local type inference

Control Flow

if (x > 0) { } else if (x == 0) { } else { }: Conditional
for (int i = 0; i < 10; i++) { }: Counting loop
foreach (var item in list) { }: Iterate a collection
var name = day switch { 1 => "Mon", _ => "?" };: Switch expression

Collections

var list = new List<int> { 1, 2, 3 };: Resizable list
var dict = new Dictionary<string, int>();: Key/value map
var set = new HashSet<string>();: Unique elements

OOP

public class Dog : Animal, IPet { }: Inheritance + interface implementation
public int Age { get; private set; }: Auto-property with a private setter
public override string ToString() => "...";: Overriding a virtual method
public record Point(int X, int Y);: Record — immutable data carrier

Exceptions & Nullability

try { Risky(); } catch (IOException e) { } finally { }: Handle a specific exception
string? name = null;: Nullable reference type
var length = name?.Length ?? 0;: Null-conditional + null-coalescing

LINQ & async

list.Where(x => x > 0).Select(x => x * 2).ToList();: Filter and transform
async Task<int> GetAsync() { return await FetchAsync(); }: Async method