C# Evolved

Records

C# 9.0 .NET 5.0

Published Updated Author Jeffrey T. Fritz Reading time —

Records are a concise way to model value-oriented data with built-in equality, deconstruction, and non-destructive mutation.

Records arrived in C# 9.0. They are designed for data shapes where the value matters more than the object identity.

Why it matters

Records reduce boilerplate for DTOs, messages, and other immutable models. The compiler gives you equality, ToString(), and with-based cloning behavior for free.

That makes them a strong default for API payloads and other data-transfer shapes.

Cautions

Records are not always the right fit. If the object has a strong identity, mutable state, or behavior-heavy responsibilities, a regular class may be a better model.

Also be careful with inheritance and equality rules when records participate in deeper type hierarchies.

Modeling immutable data with a record

Records are concise reference types with value-based equality and built-in support for non-destructive updates.

Valid since C# 9.0 

var today = new WeatherReading("Seattle", 9.5m);
var warmer = today with { TemperatureC = 12.0m };

public record WeatherReading(string City, decimal TemperatureC);

Init accessors

C# 9.0 .NET 5.0

Start with Init accessors when you want an earlier building block for Records.

Init accessors let you keep object initialization simple while still protecting properties from later mutation.

Required Members

C# 11.0 .NET 7.0

Continue to Required Members for the next guide in this theme.

Required members enforce that specific properties must be set during object initialization, preventing incomplete objects and catching errors at compile time.

Tuples

C# 7.0 NETFx 4.7

Explore Tuples for another earlier stepping stone in the same theme.

Tuples provide a lightweight syntax for grouping related values together and deconstruction enables you to unpack tuple elements into individual variables.

Primary constructors

C# 12.0 .NET 8.0

Explore Primary constructors to take the same theme one step further.

Declare constructor parameters directly in the class declaration, eliminating the need for explicit constructor bodies and field assignments.

With expressions

C# 9.0 .NET 5.0

Apply non-mutating copy updates naturally on record-based models.

With expressions let you copy immutable data and update only what changed, keeping your intent crisp and your models predictable.

Learn more

Record types (Microsoft Learn)