当响应为 HttpStatusCode.NoContent 时，有什么方法可以获取 HttpResponseMessage.Content 正文？

Question

I am using C# and .NET Core 3.0

Currently when I send GET request to a server and it returns response with status 204 , then it seems that System.Net.Http.HttpClient strips body from it and I cannot read its content.

var request = new HttpRequestMessage(HttpMethod.Get,$"/gettask.ashx?testerror=20");
var response = await _httpClient.SendAsync(request);
var responseContent = await response.Content.ReadAsStringAsync();

I know the server is returning also body when status is 204. I have tested it with Curl and it returns this body for 204 { "nextRequestInSec": 10 } .

Verbose response from curl:

curl http://address.dom/testerror=204 -v
*   Trying xxx.xxx.xxx.xxx...
* TCP_NODELAY set
* Connected to address.dom (xxx.xxx.xxx.xxx) port 80 (#0)
> GET testerror=204 HTTP/1.1
> Host: address.dom
> User-Agent: curl/7.55.1
> Accept: */*
>
< HTTP/1.1 204 No Content
< Cache-Control: private
< Transfer-Encoding: chunked
< Content-Type: text/html; charset=utf-8
< Server: Microsoft-IIS/8.5
< X-AspNet-Version: 4.0.30319
< X-Powered-By: ASP.NET
< Date: Wed, 20 Nov 2019 13:45:00 GMT
<
{ "nextRequestInSec" : 10 }* Connection #0 to host address.dom left intact

For other responses (200, 401, 403, 404, 420, 500) it works correctly and I can read body as well.

Is there any way how to get to this body?

Answer 1

As @peinarydevelopment mentions in their comment, the httpclient instance will not return a body for status codes that dont support one. The best solution to your problem is to fix the server (or ask whoever is responsible for it).

If you really must deal with the broken HTTP server, you could drop down to TCP level and retrieve the packets directly from the socket, put that seems like a very long way around the problem.

Answer 2

204 means there is no content, so before reading the content check the status code. If you want to return data, change your status code because 204 should not.

var request = new HttpRequestMessage(HttpMethod.Get,$"/gettask.ashx?testerror=20");
var response = await _httpClient.SendAsync(request);
var responseContent = (response.IsSuccessStatusCode && response.StatusCode !=204)? await 
                      response.Content.ReadAsStringAsync():null;

Answer 3

Well it appears that I was a bit blinded. The truth is that in .NET Core this is not possible according to the HttpClient

Also if You look at it as the HTTP communication, it should follow HTTP specification , which says, that:

The 204 response MUST NOT include a message-body, and thus is always terminated by the first empty line after the header fields.