[C#] Interfaces created for OneOf not implemented

[andymarshallseas]

Description

When I try to generate the C# files for the OAS spec from here (raw), the interfaces generated for the OneOf sections do not have implementations.

This interface has no implementations, so I cannot create a valid request.

Strangely, the interface created is not prefixed with I.

Have I misconfigured something? Am I using the codegen tool incorrectly? Is the OAS not well-structured?

Swagger-codegen version

3.0.54

Swagger declaration file content or url

https://digital.nhs.uk/restapi/oas/324177

Command line used for generation

java -jar .\swagger-codegen-cli.jar generate -i https://digital.nhs.uk/restapi/oas/324177 -l csharp

Steps to reproduce

1. Run command above.
2. Navigate to IO.Swagger.Model.OneOfR4PrepareBodyEntryItems