Records: value equality and with-expressions for immutable data models

Classes use reference equality by default, requiring manual Equals/GetHashCode overrides for value-based comparisons. This is boilerplate-heavy and error-prone for data transfer objects and domain value objects.

Use record types which provide structural equality, ToString, and non-destructive mutation via with:

// Positional record — concise, immutable
public record Point(double X, double Y);

var p1 = new Point(1, 2);
var p2 = new Point(1, 2);
Console.WriteLine(p1 == p2); // true — value equality

// Non-destructive mutation
var p3 = p1 with { Y = 5 }; // new Point(1, 5)

// Mutable record (record class with init)
public record PersonDto
{
    public required string Name { get; init; }
    public int Age { get; init; }
}

// Record struct — stack-allocated, no inheritance
public readonly record struct Money(decimal Amount, string Currency);

Records generate compiler-synthesized Equals, GetHashCode, and == based on all public properties. This eliminates boilerplate for DTOs, value objects, and event payloads where identity is determined by content.