Structure vs Class in C#: Key Differences Every Developer Must Know
In C#, a struct is a value type that lives wherever the variable is declared; a class is a reference type whose data sits on the managed heap while the variable keeps just a pointer.
Developers often confuse the two because they look identical: both can have fields, methods, and constructors. Yet the moment you copy or pass them around, one duplicates bytes while the other shares the same object, leading to subtle bugs.
Key Differences
Struct: value type, stack-allocated, copied by value, cannot be inherited, default constructor always exists. Class: reference type, heap-allocated, copied by reference, supports inheritance, requires explicit constructor if any is defined.
Which One Should You Choose?
Use struct for lightweight, immutable data like a 3-D point or RGB color. Reach for class when you need polymorphism, identity sharing, or large mutable state, such as a player object in a game engine.
Examples and Daily Life
Struct: Unity’s Vector3 keeps x, y, z on the stack for fast math. Class: an OrderService instance is shared across repositories, ensuring every update reflects in one place without costly copies.
Can a struct have methods?
Yes. It supports methods, properties, and even operators, but virtual methods are disallowed because structs are sealed.
Does using a class always mean slower performance?
Not necessarily. Heap allocation adds GC pressure, yet for large or shared data, reference semantics can be faster and safer than copying big structs.