C# Cheat Sheet

Free C# cheat sheet: syntax, LINQ, async/await, properties, and OOP essentials in one quick reference.

Basics

Concept	Syntax	Example
Variable	`var x = 5; int y = 10;`	`var name = "Alice";`
String interpolation	`$"text {expr}"`	`$"Hello {name}, age {age}"`
Null coalescing	`a ?? b`	`var result = input ?? "default";`
Pattern matching	`is pattern`	`if (obj is string s) Console.Write(s);`

LINQ

Concept	Syntax	Example
Where	`.Where(x => condition)`	`list.Where(x => x > 5)`
Select	`.Select(x => transform)`	`list.Select(x => x.Name)`
OrderBy	`.OrderBy(x => key)`	`list.OrderBy(x => x.Age)`
GroupBy	`.GroupBy(x => key)`	`list.GroupBy(x => x.Dept)`
Aggregate	`.Sum() .Count() .Average()`	`list.Sum(x => x.Price)`

OOP

Concept	Syntax	Example
Class	`class Name { }`	`class Dog { public string Name { get; set; } }`
Inheritance	`class B : A { }`	`class Puppy : Dog { }`
Interface	`interface IName { }`	`interface IDrawable { void Draw(); }`
Record	`record Name(params)`	`record Person(string Name, int Age);`

Collections

Concept	Syntax	Example
List	`List<T>`	`var list = new List<string> { "a", "b" };`
Dictionary	`Dictionary<K,V>`	`var dict = new Dictionary<string,int>();`
HashSet	`HashSet<T>`	`var set = new HashSet<int> { 1, 2, 3 };`

Async

Concept	Syntax	Example
Async method	`async Task<T> Method()`	`async Task<string> GetAsync() { ... }`
Await	`await asyncMethod()`	`var data = await GetDataAsync();`
Task.WhenAll	`await Task.WhenAll(t1, t2)`	`await Task.WhenAll(task1, task2);`