Server cannot set status after sending HTTP headers - CORS web api

Question

Ok, I already beat my head over this ...

Setup:

• I have a Web Api 2.0 project with basic authentication.
• I have CORS enabled in web.config
• I have ELMAH registration errors
• I have a DelegatingHandler processing an incoming request - (code below)
• I have a very specific data structure, so I do not use Microsoft membership or ID.
• I clear every request that comes with the OPTIONS verb

Problem:

I get the following error: EVERY authenticated request:

System.Web.HttpException (0x80004005): Server cannot set status after HTTP headers have been sent.
   at System.Web.HttpResponse.set_StatusCode(Int32 value)
   at System.Web.HttpResponseWrapper.set_StatusCode(Int32 value)
   at System.Web.Http.WebHost.HttpControllerHandler.<CopyResponseStatusAndHeadersAsync>d__31.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 System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at System.Web.Http.WebHost.HttpControllerHandler.<CopyResponseAsync>d__7.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 System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at System.Web.Http.WebHost.HttpControllerHandler.<ProcessRequestAsyncCore>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 System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at System.Web.TaskAsyncHelper.EndTask(IAsyncResult ar)
   at System.Web.HttpTaskAsyncHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar)

Research done so far:

The error mentioned above only occurs with the verb OPTIONS.

The error indicates that the headers have already been sent before they are asked to set their status code.

1 - elmah "SendAsync" - OPTIONS GET POST. , - OPTIONS.

, : (global.asax)

protected void Application_BeginRequest()
{
  if (Request.Headers.AllKeys.Contains("Origin") && Request.HttpMethod == "OPTIONS")
    {
        Response.Flush();
    }
}

, OPTIONS , , , :

//Capture incoming request by overriding SendAsync method

protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
    //validate credentials, set CurrentPrincipal and Current.User if valid
    if (ValidateCredentials(request.Headers.Authorization))
    {
        Thread.CurrentPrincipal = new MyPrincipal(_userName);
        HttpContext.Current.User = new MyPrincipal(_userName);
    }


    // Execute base.SendAsync to execute default actions
    // and once it is completed, capture the response object and add
    // WWW-Authenticate header if the request was marked as (401) unauthorized.

    return base.SendAsync(request, cancellationToken).ContinueWith(task =>
    {
        HttpResponseMessage response = task.Result;
        if (response.StatusCode == HttpStatusCode.Unauthorized && !response.Headers.Contains("WWW-Authenticate"))
        {
            response.Headers.Add("WWW-Authenticate", "Basic");
        }
        return response;
    });

}

, OPTIONS 405 - , elmah, 500. - HTTP-.

OPTIONS , 405, .

- ? Confused.

my cors:

<!-- BEGIN: Enable CORS -->
<httpProtocol>
  <customHeaders>
    <add name="Access-Control-Allow-Origin" value="*" />
    <add name="Access-Control-Allow-Headers" value="accept, authorization, origin, content-type" />
    <add name="Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
  </customHeaders>
</httpProtocol>

<handlers>
  <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
  <remove name="OPTIONSVerbHandler" />
  <remove name="TRACEVerbHandler" />
  <remove name="WebDAV"/>
  <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
</handlers>
<!-- END: Enable CORS -->

"FatalError", - , -, , - ? ! !

- , , IIS, , , ?

, , , ? ? ? ...

, Stack Overflow...

HELP!!!!!!!

Answer 1

a Response.End(); Response.Flush();

, .

, .