.NET Service reference sending wrong accept header (text/plain)

Question

I've created an ASP.NET Core web application, and installed + used the Swashbuckle.AspNetCore version 6.1.5 Nuget package. This hosts the following openapi document on https://example.com/swagger/v1/swagger.json.

Also my API supports content-negotiation.

• When sending no Accept header, or Accept: text/xml header, the api will return an XML string
• When sending an Accept: application/json header, the api will return a JSON string

Now I've tried consuming my api through the swagger document:

• Create a new .NET Core console application
• Right-click the project file → Add → Service Reference
• OpenAPI
  • URL: https://example.com/swagger/v1/swagger.json
  • Namespace: Example.Api
  • Class name: ExampleClient

You can then write a Main like this:

static async Task Main(string[] args)
{
    Console.WriteLine("Hello World!");
    var httpClient = new System.Net.Http.HttpClient();
    // httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
    var mintPlayerClient = new MintPlayer.Api.MintPlayerClient("https://mintplayer.com", httpClient);
    var artists = await mintPlayerClient.ApiArtistListAsync(false);
}

Now when you debug the console app

• navigate to the ApiArtistListAsync method in the swaggerClient class
• put a breakpoint at the client_.SendAsync call
• you can now inspect what the swaggerClient is sending to the webservice

Usually it's like this:

• SOAP = XML
• REST = JSON

Even when adding a DefaultRequestHeader on the HttpClient the response from the HttpClient is an XML, because it's explicitly added inside the SwaggerClient method:

And here is how the code is generated + the line where the Accept header is explicitly set (swaggerClient:430). This is auto-generated code from adding the service-reference.

So why is the Accept header in the generated code explicitly set to text/plain? Why isn't the default accept header value application/json, since this is a REST service?

Answer 1

I think you might want to check this on both side, client(your console) and server(your api project).

We all know that usually

• SOAP = XML
• REST = JSON

But you're coding the whole things, total in-control of what being send and what being response.

Let's assume you client send Accept-Header which support both text/xml and text/plain (which as i understand here, you expect a response as text/plain).

Then the server realize that your console is happy with either text/xml and text/plain, and the server itself support all kind of common format.

So it'll have to electing the most convenient format to response to the client. Which in this case is text/xml. That's so, the console received and happy with text/xml response format either way

And if that's the case, that I get you right, you want to receive text/plain on the console, then make sure the only Accept header sending out is text/plain or do some custom logic on your API to choose the text/plain format over others when sending response.

Answer 2

If you don't need "plain/text" output format, you can remove "plain/text" output formatter using :

services.AddMvc(options =>
{
    options.OutputFormatters.RemoveType<StringOutputFormatter>();
})