Why Response Redirect causes System Threading ThreadAbortException

Question

When I use Response Redirect      to redirect my form to a new page I get the error      A first chance exception of type  System Threading ThreadAbortException  occurred in mscorlib dll       An exception of type  System Threading ThreadAbortException  occurred in mscorlib dll but was not handled in user code   My understanding of this is that the error is being caused by the webserver aborting the remainder of the page the response redirect was called on   I know I can add a second parameter to Response Redirect that is called endResponse   If I set endResponse to True I still get the error but if I set it to False then I do not   I am pretty sure though that that means the webserver is running the rest of the page I redirected away from   Which would seem to be inefficient to say the least   Is there a better way to do this   Something other than Response Redirect or is there a way to force the old page to stop loading where I will not get a ThreadAbortException

User · Accepted Answer

The correct pattern is to call the Redirect overload with endResponse=false and make a call to tell the IIS pipeline that it should advance directly to the EndRequest stage once you return control:

Response.Redirect(url, false);
Context.ApplicationInstance.CompleteRequest();

This blog post from Thomas Marquardt provides additional details, including how to handle the special case of redirecting inside an Application_Error handler.

User · Answer

There is no simple and elegant solution to the Redirect problem in ASP Net WebForms  You can choose between the Dirty solution and the Tedious solution  Dirty  Response Redirect url  sends a redirect to the browser  and then throws a ThreadAbortedException to terminate the current thread  So no code is executed past the Redirect  -call  Downsides  It is bad practice and have performance implications to kill threads like this  Also  ThreadAbortedExceptions will show up in exception logging   Tedious  The recommended way is to call Response Redirect url  false  and then Context ApplicationInstance CompleteRequest   However  code execution will continue and the rest of the event handlers in the page lifecycle will still be executed   E g  if you perform the redirect in Page Load  not only will the rest of the handler be executed  Page PreRender and so on will also still be called - the rendered page will just not be sent to the browser  You can avoid the extra processing by e g  setting a flag on the page  and then let subsequent event handlers check this flag before before doing any processing    The documentation to CompleteRequest states that it  Causes ASP NET to bypass all events and filtering in the HTTP pipeline chain of execution   This can easily be misunderstood  It does bypass further HTTP filters and modules  but it doesn t bypass further events in the  current page lifecycle    The deeper problem is that WebForms lacks a level of abstraction  When you are in a event handler  you are already in the process of building a page to output  Redirecting in an event handler is ugly because you are terminating a partially generated page in order to generate a different page  MVC does not have this problem since the control flow is separate from rendering views  so you can do a clean redirect by simply returning a RedirectAction in the controller  without generating a view

User · Answer

i even tryed to avoid this  just in case doing the Abort on the thread manually  but i rather leave it with the  CompleteRequest  and move on - my code has return commands after redirects anyway  So this can be done  public static void Redirect string VPathRedirect  global  System Web UI Page Sender        Sender Response Redirect VPathRedirect  false       global  System Web UI HttpContext Current ApplicationInstance CompleteRequest

User · Answer

Here s the official line on the problem  I couldn t find the latest  but I don t think the situation has changed for later versions of  net

User · Answer

I know I m late  but I ve only ever had this error if my Response Redirect is in a Try   Catch block  Never put a Response Redirect into a Try   Catch block  It s bad practice As an alternative to putting the Response Redirect into the Try   Catch block  I d break up the method function into two steps   inside the Try   Catch block performs the requested actions and sets a  quot result quot  value to indicate success or failure of the actions   outside of the Try   Catch block does the redirect  or doesn t  depending on what the  quot result quot  value is    This code is far from perfect and probably should not be copied since I haven t tested it  public void btnLogin Click UserLoginViewModel model        bool ValidLogin   false     this is our  quot result value quot      try               using  Context Db   new Context                        User User   new User                 if  String IsNullOrEmpty model EmailAddress                   ValidLogin   false     no email address was entered             else                 User   Db FirstOrDefault x   gt  x EmailAddress    model EmailAddress                if  User    null  amp  amp  User PasswordHash    Hashing CreateHash model Password                   ValidLogin   true     login succeeded                     catch  Exception ex                throw ex     something went wrong so throw an error            if  ValidLogin                GenerateCookie User           Response Redirect  quot   Members Default aspx quot              else                  do something to indicate that the login failed

User · Answer

Also I tried other solution  but some of the code executed after redirect   public static void ResponseRedirect HttpResponse iResponse  string iUrl                ResponseRedirect iResponse  iUrl  HttpContext Current              public static void ResponseRedirect HttpResponse iResponse  string iUrl  HttpContext iContext                iResponse Redirect iUrl  false            iContext ApplicationInstance CompleteRequest             iResponse BufferOutput   true          iResponse Flush            iResponse Close            So if need to prevent code execution  after redirect   try        other code    Response Redirect          code not to be executed   catch ThreadAbortException     do there id nothing here catch Exception ex        Logging

User · Answer

This is just how Response Redirect url  true   works  It throws the ThreadAbortException to abort the thread  Just ignore that exception   I presume it is some global error handler logger where you see it    An interesting related discussion Is Response End   Considered Harmful

User · Answer

What I do is catch this exception  together with another possible exceptions  Hope this help someone    catch  ThreadAbortException ex1         writeToLog ex1 Message       catch Exception ex          writeToLog ex Message

User · Answer

Response Redirect   throws an exception to abort the current request   This KB article describes this behavior  also for the Request End   and Server Transfer   methods    For Response Redirect   there exists an overload   Response Redirect String url  bool endResponse    If you pass endResponse false  then the exception is not thrown  but the runtime will continue processing the current request    If endResponse true  or if the other overload is used   the exception is thrown and the current request will immediately be terminated

User · Answer

I had that problem too   Try using Server Transfer instead of Response Redirect  Worked for me

[c#] Why Response.Redirect causes System.Threading.ThreadAbortException?

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