Variables & Data Types

C# is a strongly typed language. Every variable has a type that determines what values it can hold.

Value types store data directly on the stack:

int count = 42;
double price = 9.99;
bool isActive = true;
char grade = 'A';
decimal salary = 75_000.50m;

Reference types store a pointer to data on the heap:

string name = "Andi";
object obj = 42;       // boxed int
int[] numbers = { 1, 2, 3 };

The compiler can infer the type from the right-hand side:

var message = "Hello";   // string
var total = 100;         // int
var items = new List<string>();  // List<string>

var is not dynamic — the type is determined at compile time. Use it when the type is obvious from context.

Value types can be made nullable with ?:

int? age = null;
if (age.HasValue)
    Console.WriteLine(age.Value);