How C# record class and record struct differ from standard classes:

public record User(int Id, string Username, string Email);

Compiler-Synthesized Features:

1. Value-Based Equality: Two record instances with identical property values compare equal (user1 == user2 is true).
2. Non-Destructive Mutation (with expression): var updated = user with { Email = "new@domain.com" };
3. Deconstruction: var (id, name, email) = user;
4. Formatted ToString(): Automatically prints User { Id = 1, Username = Alice, Email = ... } for clean logging.

Use record struct when you want lightweight value semantics without heap allocations, and record class for immutable reference data transfer objects (DTOs).

The with expression performs a memberwise clone under the hood and applies the specified property overrides cleanly.