Correct way to return HttpResponseMessage as IActionResult in .Net Core 2.2

Question

In .Net Core 2.2. I am creating a API Controller that routes the request to another Http endpoint based on payload.

  [Route("api/v1")]
  public class RoutesController : Controller
  {
      [HttpPost]
      [Route("routes")]
      public async Task<IActionResult> Routes([FromBody]JObject request)
      {
                 
        var httpClient = new HttpClient();

        // here based on request httpCLient will make `POST` or `GET` or `PUT` request
        // and returns `Task<HttpResponseMessage>`. Lets assume its making `GET` 
        // call

       Task<HttpResponseMessage> response = await
         httpClient.GetAsync(request["resource"]);
            
       /*  ??? what is the correct way to return response as `IActionResult`*/
      }        
  }

based on SO post i can do this

        return StatusCode((int)response.StatusCode, response);

However i am not sure sending HttpResponseMessage as ObjectResult is correct way.

I also want to make sure content negotiation will work.

Answer 1

public class HttpResponseMessageResult : IActionResult
{
    private readonly HttpResponseMessage _responseMessage;

    public HttpResponseMessageResult(HttpResponseMessage responseMessage)
    {
        _responseMessage = responseMessage; // could add throw if null
    }

    public async Task ExecuteResultAsync(ActionContext context)
    {
        var response = context.HttpContext.Response;


        if (_responseMessage == null)
        {
            var message = "Response message cannot be null";

            throw new InvalidOperationException(message);
        }

        using (_responseMessage)
        {
            response.StatusCode = (int)_responseMessage.StatusCode;

            var responseFeature = context.HttpContext.Features.Get<IHttpResponseFeature>();
            if (responseFeature != null)
            {
                responseFeature.ReasonPhrase = _responseMessage.ReasonPhrase;
            }

            var responseHeaders = _responseMessage.Headers;

            // Ignore the Transfer-Encoding header if it is just "chunked".
            // We let the host decide about whether the response should be chunked or not.
            if (responseHeaders.TransferEncodingChunked == true &&
                responseHeaders.TransferEncoding.Count == 1)
            {
                responseHeaders.TransferEncoding.Clear();
            }

            foreach (var header in responseHeaders)
            {
                response.Headers.Append(header.Key, header.Value.ToArray());
            }

            if (_responseMessage.Content != null)
            {
                var contentHeaders = _responseMessage.Content.Headers;

                // Copy the response content headers only after ensuring they are complete.
                // We ask for Content-Length first because HttpContent lazily computes this
                // and only afterwards writes the value into the content headers.
                var unused = contentHeaders.ContentLength;

                foreach (var header in contentHeaders)
                {
                    response.Headers.Append(header.Key, header.Value.ToArray());
                }

                await _responseMessage.Content.CopyToAsync(response.Body);
            }
        }
    }