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Data Types

By · Reviewed & last updated · Part of C# Tutorial

C# has two top-level type families: value types (numbers, structs, enums — stored inline) and reference types (classes, strings, arrays, delegates — stored on the heap, accessed via a reference).

Value types vs reference types

EXAMPLE
// Value types — small, copied on assignment
int     age   = 36;
double  pi    = 3.14159;
decimal money = 99.95m;     // exact decimal
bool    ok    = true;
char    c     = 'A';
struct  Point { public int X, Y; }

// Reference types — accessed through references
string  s     = "Ada";
int[]   nums  = { 1, 2, 3 };
List<int> list = new();
class User { public string Name { get; set; } }

// Records — reference types with value equality + with-syntax
public record Person(string Name, int Age);
var p1 = new Person("Ada", 36);
var p2 = p1 with { Age = 37 };       // immutable copy
Console.WriteLine(p1 == new Person("Ada", 36));   // True (value equality)

// Nullable reference types — enable in csproj
string? maybe = null;
int len = maybe?.Length ?? 0;

Why it matters

Use decimal (not double) for money. Use record for immutable data carriers. Turn nullable reference types ON in every new project.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
byte    b = 1;
int     i = 10;
long    l = 99L;
float   f = 1.5f;
double  d = 2.5;
decimal m = 9.99m;
bool    t = true;
char    c = 'A';
Try it Yourself »

Discussion

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