JsonPolymorph 1.1.3

JsonPolymorph

JsonPolymorph is a .NET helper library to simplify generating polymorphic JSON models from C# record hierarchies. It is intended to be used with NSwag to generate OpenAPI v3 schemas and client-side code for ASP.NET Core web APIs that properly round-trips C# record hierarchies to and from JSON.

Usage

Installation is via the JsonPolymorph NuGet package.

A simple example:

[JsonHierarchyBase]
public abstract partial record VehicleCommand();
public sealed record TurnLeft() : VehicleCommand;
public sealed record TurnRight() : VehicleCommand;

Applying the JsonHierarchyBaseAttribute to a type will cause the following attributes to be added at compile time:

• An instance of JsonConverterAttribute with a hardcoded JSON discriminator property name, i.e. [Newtonsoft.Json.JsonConverter(typeof(NJsonSchema.Converters.JsonInheritanceConverter), "discriminator")]
• For every type DerivedRecordType in the assembly that is derived from the target, an instance of KnownTypeAttribute, i.e. [System.Runtime.Serialization.KnownType(typeof(DerivedRecordType))]

Applying this attribute is only supported at the base level of the hierarchy, i.e. a record directly derived from object.

Credits

Many thanks to Jonathan Allen (@Grauenwolf) for the fantastic InfoQ article and sample code that served as the inspiration for this project.