Value types vs reference types — C# Language — Basics to Advanced

4. Value types vs reference types

Basic★ Must knowLesson 4 of 38

	Value types	Reference types
Examples	`int`, `double`, `bool`, `char`, `decimal`, `struct`, `enum`, `DateTime`	`class`, `string`, arrays, `delegate`, `interface`, `record` (class)
Variable holds	The data itself	A reference (address) to an object on the heap
Assignment	Copies the value	Copies the reference — both point to the same object
Default	`0`, `false`, ...	`null`
Stored	Inline: on the stack for locals, inside the containing object for fields	Object on the managed heap

csharp

struct Point { public int X; }
class Box { public int X; }

var p1 = new Point { X = 1 };
var p2 = p1;      // copy
p2.X = 99;
Console.WriteLine(p1.X); // 1

var b1 = new Box { X = 1 };
var b2 = b1;      // same object
b2.X = 99;
Console.WriteLine(b1.X); // 99

Interview tip: "Value types live on the stack" is only partly true. A value-type field inside a class lives on the heap with that object. Say: value types are stored inline where they are declared.