When to use struct vs class

Context: Choosing between struct and class depends on the intended use, size, and behavior requirements.

Use a `struct` when:

The instance is small (≤ 16 bytes typically)
The type is immutable (or should have value semantics)
You need value equality (copies are independent)
Performance requires stack allocation (e.g., many short‑lived instances)
The type is used in performance‑critical paths

Use a `class` when:

The type is large (> 16 bytes)
You need reference semantics (sharing, identity)
Inheritance is required
You need to use the type with null checks (reference types)
The object will be stored in collections frequently (boxing overhead for structs)

Guidelines

Feature	Struct	Class
Type	Value type	Reference type
Allocation	Stack / inline	Heap
Inheritance	No (except interfaces)	Yes
Default equality	Value‑based	Reference‑based
Nullable	`Nullable<T>` or `T?`	Directly `null`

// Good struct candidate: small, immutable, value semantics
public readonly struct Point(int X, int Y);

// Good class candidate: large, mutable, needs identity
public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    // ...
}

Real-world usage example

Database entities: Use classes because they have identity (database primary key) and are often large. Value objects (like Money, Address) are better as structs or records.

Example: In Entity Framework Core, entities are classes. Value objects can be implemented as struct or record struct.

When to use struct vs class

Use a struct when:

Use a class when:

Guidelines

Real-world usage example

Related sections

Use a `struct` when:

Use a `class` when: