Lesson 15 of 40 Core C# Intermediate ⏱ 30 min

Structs, Records & Value Types

Choose the right type for the job — structs for stack-allocated value semantics, records for immutable data, and understand boxing/unboxing.

Part 1: struct vs class

Feature	struct	class
Allocation	Stack (usually)	Heap
Equality	Value equality	Reference equality (by default)
Default	All fields = default	null
Inheritance	No class inheritance	Yes
Use when	Small, short-lived data	Complex objects with behavior

Part 2: readonly struct

public readonly struct Money
{
    public decimal Amount { get; }
    public string Currency { get; }
    public Money(decimal amount, string currency)
        => (Amount,Currency) = (amount,currency);
    public Money Add(Money other) => new(Amount + other.Amount, Currency);
}

Part 3: record and record struct

// Positional record — auto property, equality, ToString
public record Person(string Name, int Age);

// Non-destructive mutation (with expression)
var alice = new Person("Alice", 30);
var olderAlice = alice with { Age = 31 };

// record struct — stack allocated, value equality
public record struct Point(double X, double Y);

Part 4: Boxing & Unboxing

// Boxing — value type → object (heap allocation!)
int x = 42;
object boxed = x; // boxed

// Unboxing — cast back
int unboxed = (int)boxed;

// Avoid boxing in hot paths!
// Use List<int> not ArrayList for int storage
// Use generic constraints instead of object params

Structs, Records & Value Types

Part 1: struct vs class

Part 2: readonly struct

Part 3: record and record struct

Part 4: Boxing & Unboxing

C# in Visual Studio 2026