title: Server cannot set status after HTTP headers have been sent IIS7.5
body: <p>Sometimes I get exception in my production environment:</p>
  
  <blockquote>
    <ul>
    <li><strong>Process information</strong> 
    
    <ul>
    <li>Process ID: 3832  </li>
    <li>Process name: w3wp.exe </li>
    <li>Account name: NT AUTHORITY\NETWORK SERVICE  </li>
    </ul></li>
    <li><strong>Exception information</strong>
    
    <ul>
    <li>Exception type: System.Web.HttpException   </li>
    <li>Exception message: <strong>Server cannot set status after HTTP headers have been sent.</strong>  </li>
    </ul></li>
    <li><strong>Request information</strong>
    
    <ul>
    <li>Request URL: <a href="http://www.myulr.pl/logon" rel="noreferrer">http://www.myulr.pl/logon</a>  </li>
    <li>Request path: /logon  </li>
    <li>User host address: 10.11.9.1    </li>
    <li>User: user001  </li>
    <li>Is authenticated: True   </li>
    <li>Authentication Type: Forms   </li>
    <li>Thread account name: NT AUTHORITY\NETWORK SERVICE   </li>
    </ul></li>
    <li><strong>Thread information</strong>
    
    <ul>
    <li>Thread ID: 10   </li>
    <li>Thread account name: NT AUTHORITY\NETWORK SERVICE   </li>
    <li>Is impersonating: False </li>
    </ul></li>
    </ul>
  </blockquote>
  
  <pre><code>Stack trace: at System.Web.HttpResponse.set_StatusCode(Int32 value) at  
  System.Web.HttpResponseWrapper.set_StatusCode(Int32 value) at  
  System.Web.Mvc.HandleErrorAttribute.OnException(ExceptionContext filterContext) at  
  System.Web.Mvc.ControllerActionInvoker.InvokeExceptionFilters(ControllerContext controllerContext, IList(1) filters, Exception exception) at  
  System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) at System.Web.Mvc.Controller.ExecuteCore() at  
  System.Web.Mvc.MvcHandler.&lt;&gt;c__DisplayClass8.&lt;BeginProcessRequest&gt;b__4() at  
  System.Web.Mvc.Async.AsyncResultWrapper.&lt;&gt;c__DisplayClass1.&lt;MakeVoidDelegate&gt;b__0() at  
  System.Web.Mvc.Async.AsyncResultWrapper.&lt;&gt;c__DisplayClass8(1).&lt;BeginSynchronous&gt;b__7(IAsyncResult _) at  
  System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult(1).End() at   
  System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) at  
  System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at  
  System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; ompletedSynchronously) 
  </code></pre>
  
  <p>I didn't noticed this error on my test environment what should I check?</p>
  
  <p><strong>I am using ASP.NET MVC 2 (Release Candidate 2)</strong> </p>