Server cannot append header after HTTP headers have been sent uploading files

Question

I get this exception intermittently in my asp.net mvc 5 c# web application:

Server cannot append header after HTTP headers have been sent.

It just happens uploading images to S3 method (Web Api Controller).

The presendrequestheaders in Global.asax

protected void Application_PreSendRequestHeaders(object sender, EventArgs e)
        {
            HttpApplication app = sender as HttpApplication;
            if (app != null &&
                app.Context != null)
            {
                app.Context.Response.Headers.Remove("Server");
            }
        }

The method that trigger the error:

    [HttpPost]
    [Route("UploadImageJSON")]
    public IHttpActionResult UploadImageJSON(HttpRequestMessage request)
    {
        var httpRequest = HttpContext.Current.Request;

        // Check if files are available
        if (httpRequest.Files.Count != 1) return BadRequest();

        var postedFile = httpRequest.Files[0];

        var contentType = postedFile.ContentType;
        if (!contentType.Contains("image"))
        {
            return StatusCode(HttpStatusCode.NotAcceptable);
        }




        var keyUploadFiles = Constants.UrlS3Amazon +
                             S3.UploadToS3WithStream(postedFile.InputStream, contentType);


        return Json(JsonConvert.SerializeObject(keyUploadFiles));


    }

EDIT: More information... I have my Web App hosted in Elastic BeanStalk with a load balancer, the load balancer has installed a SSL Certificate, and the connection between the load balancer and the EC2 instances are in ports 80. Maybe it could be helpful.

The Elmah log:

System.Web.HttpException (0x80004005): Server cannot append header after HTTP headers have been sent. at System.Web.HttpHeaderCollection.SetHeader(String name, String value, Boolean replace) at Microsoft.Owin.Host.SystemWeb.CallHeaders.AspNetResponseHeaders.Set(String key, String[] values) at Microsoft.Owin.Infrastructure.OwinHelpers.AppendHeaderUnmodified(IDictionary2 headers, String key, String[] values) at Microsoft.Owin.ResponseCookieCollection.Append(String key, String value, CookieOptions options) at Microsoft.Owin.Security.Cookies.CookieAuthenticationHandler.<ApplyResponseGrantAsync>d__b.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.<ApplyResponseCoreAsync>d__8.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationHandler.<TeardownAsync>d__5.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Security.Infrastructure.AuthenticationMiddleware1.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Identity.Owin.IdentityFactoryMiddleware2.<Invoke>d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Identity.Owin.IdentityFactoryMiddleware2.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNet.Identity.Owin.IdentityFactoryMiddleware`2.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Owin.Mapping.MapMiddleware.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.EndFinalWork(IAsyncResult ar) at System.Web.HttpApplication.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Thanks!!

Answer 1

have you tried with removing app.Context.Response.Headers.Remove("Server"); i think there is this is the issue?