I found product like REST United, Swagger, Alpaca, IO-docs, Google API client generator and Postman but they seems to be more documentation or REST client SDK generators. I'looking for the server side REST API generator.
I'm looking for something that should be able to connect to my database and let me choose for which table or view I want a readone/readpage/readall/create/update/delete request.
I think your issue might be that you're trying to use a stateful collection in a stateless context. You can use it for event handling on your UX, but it should be immaterial on the WebAPI. Have you tried setting your expected parameter as Collection or ICollection?