[C#] Invalid code produced for Multipart File with json generated by springdoc

Description

I have a Spring Boot REST Api that is using springdoc-openapi to generate the json file.

I have then tried to generate a client for this api with swagger-codegen version 3.0.22 and latest commit from the 3.0.0 branch and both produced invalid code.

The problem is for an endpoint that wants a file. swagger-codegen uses a variable named _file in the body of the corresponding methods but does not declare it as a parameter of the method, the variable then stays undeclared.

The problem could either be in swagger-codegen itself or my usage of springdoc.

Swagger-codegen version

Version 3.0.22 and reproduced with latest commit from 3.0.0 branch (ad1b8bb54ce5eb1677426b5a49e80102590badc1)

Swagger declaration file content or url

https://gist.github.com/LelouBil/cf5171e879c1003216b1e70ae5c61c5d

Command line used for generation

"java.exe","-jar swagger-codegen-cli.jar generate -i http://localhost:8080/v3/api-docs -l csharp -o output

Steps to reproduce

This example project has the same problem

DemoSpringApp.zip

Reproduce with swagger-codegen 3.0.22 or the 3.0.0 branch using the linked springdoc-generated OpenAPI document, the DemoSpringApp.zip example, and the csharp generator command. Inspect the C# generator entry points and templates for the multipart file endpoint; done means the generated methods declare every referenced file variable and produce valid C#.