[REQ] Allow extensibility for C# clients

Is your feature request related to a problem? Please describe.

We’re having trouble using the generated .NET clients. It seems they are not open to extension like other client libraries. Specifically, all abstractions (Configuration, IApiAccessor, etc.) are generated within the client rather than factored out to a common library that extensions can rely on.

Describe the solution you’d like

• Publish an official library for base abstractions that generated client libraries depend on.
• Support a client constructor that accepts an HttpClient so that the official client extensibility points can be leveraged.

Describe alternatives you’ve considered

From a first principles perspective, I don’t think other solutions are possible without providing base abstractions. We will likely evaluate other generators or write our own.

Additional context

Providing extensibility would close #3581.

[devhl-labs]

I didn’t write the httpclient library, but I believe it is the same as the default restsharp, just patched to force it to use HttpClient. My generichost library is a complete rewrite at this point. The clients are added to the host in the ConfigureApi method. What you are showing here is only the user provided Action, it’s not all that happens. The clients are registered as singletons (will become transient once my PRs are merged).

[devhl-labs]

Sure, see here the library option. https://openapi-generator.tech/docs/generators/csharp-netcore