Merge pull request #7004 from Particular/record-types

Support for `record` types

Author: tmasternak

nservicebus/messaging/immutable-messages.md

@@ -1,6 +1,6 @@
 ---
 title: Immutable Messages
-reviewed: 2024-08-13
+reviewed: 2025-02-19
 component: Core
 related:
 - samples/immutable-messages
@@ -13,8 +13,19 @@ Usually messages are designed as [DTOs](https://en.wikipedia.org/wiki/Data_trans
 
 Message objects can be made immutable at runtime by:
 
-1. Creating properties with only public getters and initializing these properties via constructor initialization.
-2. Having regular message classes with public getters/setters at the sender, where these classes implement an interface with only public getters. Receivers reference only the interface.
+1. Using record types
+2. Creating properties with only public getters and initializing these properties via constructor initialization.
+3. Having regular message classes with public getters/setters at the sender, where these classes implement an interface with only public getters. Receivers reference only the interface.
+
+
+## Record types
+
+> [!NOTE]
+> Record types are supported starting with NServiceBus 9
+
+```c#
+public record CancelOrder(int OrderId);
+```
 
 ## Properties with only public getters
 

nservicebus/messaging/messages-events-commands.md

@@ -49,14 +49,15 @@ There are checks in place to ensure best practices are followed. Violations of t
 
 Messages should:
 
-* Be simple [POCO](https://en.wikipedia.org/wiki/Plain_old_CLR_object) types
+* Be simple [POCOs](https://en.wikipedia.org/wiki/Plain_old_CLR_object) of type `class`, `struct`, or `record`.
 * Be as small as possible
 * Satisfy the [Single Responsibility Principle](https://en.wikipedia.org/wiki/Single_responsibility_principle)
 * Favor simplicity and redundancy over object-oriented practices like inheritance
 * Not be re-used for other purposes (e.g., domain objects, data access objects, or UI binding objects)
 
 > [!NOTE]
-> Prior to NServiceBus version 7.2, messages had to be defined as a `class`. Defining them as a `struct` would result in a runtime exception.
+> - `struct` is supported since 7.2+.
+> - `record` is supported since 9.0+.
 
 Generic message definitions (e.g., `MyMessage<T>`) are not supported. It is recommended to use dedicated, simple types for each message.