Can't read HttpResponseMessage content when the status code is not success

Question

I have a service which is consuming an SMS REST API using HttpClient:

HttpClient http = this._httpClientFactory.CreateClient();
// Skipped: setup HttpRequestMessage
using (HttpResponseMessage response = await http.SendAsync(request))
{
    try
    {
        _ = response.EnsureSuccessStatusCode();
    }
    catch (HttpRequestException)
    {
        string responseString = await response.Content.ReadAsStringAsync(); // Fails with ObjectDisposedException
        this._logger.LogInformation(
            "Received invalid HTTP response status '{0}' from SMS API. Response content was {1}.",
            (int)response.StatusCode,
            responseString
        );
        throw;
    }
}

The API returns an error, but I would like to be able to log it. So I need to log both the failing status code (which I can read from response.StatusCode) and the associated content (which may contain additional error useful details).

This code fails on the instruction await response.Content.ReadAsStringAsync() with this exception:

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'System.Net.Http.HttpConnection+HttpConnectionResponseContent'.
    Module "System.Net.Http.HttpContent", in CheckDisposed
    Module "System.Net.Http.HttpContent", in ReadAsStringAsync

Some sources suggest that you shouldn't read the response content when the status code is not in the success range (200-299), but what if the response really contains useful error details?

.NET version used: .NET Core 2.1.12 on AWS lambda linux runtime.

Answer 1

OK, apparently this is a known issue in the .NET API, which has been addressed in .NET Core 3.0. response.EnsureSuccessStatusCode() is actually disposing the response content. It was implemented this way to supposedly help users:

// Disposing the content should help users: If users call EnsureSuccessStatusCode(), an exception is
// thrown if the response status code is != 2xx. I.e. the behavior is similar to a failed request (e.g.
// connection failure). Users don't expect to dispose the content in this case: If an exception is
// thrown, the object is responsible fore cleaning up its state.

This is an undesirable behavior which was removed from 3.0. In the meantime, I just switched to use IsSuccessStatusCode before the log:

HttpClient http = this._httpClientFactory.CreateClient();
// Skipped: setup HttpRequestMessage
using (HttpResponseMessage response = await http.SendAsync(request))
{
    if (!response.IsSuccessStatusCode)
    {
        string responseString = await response.Content.ReadAsStringAsync(); // Fails with ObjectDisposedException
        this._logger.LogInformation(
            "Received invalid HTTP response status '{0}' from SMS API. Response content was {1}.",
            (int)response.StatusCode,
            responseString
        );
        _ = response.EnsureSuccessStatusCode();
    }
}

A little bit more redundant, but it should work.