ASP NET custom error page - Server GetLastError is null

Question

I have a custom error page set up for my application    lt customErrors mode  On  defaultRedirect    errors GeneralError aspx    gt    In Global asax  Application Error    the following code works to get the exception details     Exception ex   Server GetLastError      if  ex    null                if  ex GetBaseException      null              ex   ex GetBaseException            By the time I get to my error page    errors GeneralError aspx cs   Server GetLastError   is null  Is there any way I can get the exception details on the Error Page  rather than in Global asax cs    ASP NET 3 5 on Vista IIS7

User · Answer

One important consideration that I think everybody is missing here is a load-balancing (web farm) scenario. Since the server that's executing global.asax may be different than the server that's about the execute the custom error page, stashing the exception object in Application is not reliable.

I'm still looking for a reliable solution to this problem in a web farm configuration, and/or a good explanation from MS as to why you just can't pick up the exception with Server.GetLastError on the custom error page like you can in global.asax Application_Error.

P.S. It's unsafe to store data in the Application collection without first locking it and then unlocking it.

User · Answer

Looking more closely at my web config set up  one of the comments in this post is very helpful     in asp net 3 5 sp1 there is a new parameter redirectMode   So we can amend customErrors to add this parameter    lt customErrors mode  RemoteOnly  defaultRedirect    errors GeneralError aspx  redirectMode  ResponseRewrite    gt    the ResponseRewrite mode allows us to load the   Error Page   without redirecting the browser  so the URL stays the same  and importantly for me  exception information is not lost

User · Answer

A combination of what NailItDown and Victor said  The preferred easiest way is to use your Global Asax to store the error and then redirect to your custom error page    Global asax       void Application Error object sender  EventArgs e            Code that runs when an unhandled error occurs     Exception ex   Server GetLastError        Application  TheException     ex    store the error for later     Server ClearError      clear the error so we can continue onwards     Response Redirect    myErrorPage aspx      direct user to error page     In addition  you need to set up your web config      lt system web gt       lt customErrors mode  RemoteOnly  defaultRedirect    myErrorPage aspx  gt       lt  customErrors gt     lt  system web gt    And finally  do whatever you need to with the exception you ve stored in your error page   protected void Page Load object sender  EventArgs e                do stuff           we caught an exception in our Global asax  do stuff with it      Exception caughtException    Exception Application  TheException              do stuff

User · Answer

A combination of what NailItDown and Victor said  The preferred easiest way is to use your Global Asax to store the error and then redirect to your custom error page    Global asax       void Application Error object sender  EventArgs e            Code that runs when an unhandled error occurs     Exception ex   Server GetLastError        Application  TheException     ex    store the error for later     Server ClearError      clear the error so we can continue onwards     Response Redirect    myErrorPage aspx      direct user to error page     In addition  you need to set up your web config      lt system web gt       lt customErrors mode  RemoteOnly  defaultRedirect    myErrorPage aspx  gt       lt  customErrors gt     lt  system web gt    And finally  do whatever you need to with the exception you ve stored in your error page   protected void Page Load object sender  EventArgs e                do stuff           we caught an exception in our Global asax  do stuff with it      Exception caughtException    Exception Application  TheException              do stuff

User · Answer

Looking more closely at my web config set up  one of the comments in this post is very helpful     in asp net 3 5 sp1 there is a new parameter redirectMode   So we can amend customErrors to add this parameter    lt customErrors mode  RemoteOnly  defaultRedirect    errors GeneralError aspx  redirectMode  ResponseRewrite    gt    the ResponseRewrite mode allows us to load the   Error Page   without redirecting the browser  so the URL stays the same  and importantly for me  exception information is not lost

User · Answer

OK  I found this post  http   msdn microsoft com en-us library aa479319 aspx  with this very illustrative diagram     source  microsoft com     in essence  to get at those exception details i need to store them myself in Global asax  for later retrieval on my custom error page    it seems the best way is to do the bulk of the work in Global asax  with the custom error pages handling helpful content rather than logic

User · Answer

One important consideration that I think everybody is missing here is a load-balancing (web farm) scenario. Since the server that's executing global.asax may be different than the server that's about the execute the custom error page, stashing the exception object in Application is not reliable.

I'm still looking for a reliable solution to this problem in a web farm configuration, and/or a good explanation from MS as to why you just can't pick up the exception with Server.GetLastError on the custom error page like you can in global.asax Application_Error.

P.S. It's unsafe to store data in the Application collection without first locking it and then unlocking it.

User · Answer

I think you have a couple of options here   you could store the last Exception in the Session and retrieve it from your custom error page  or you could just redirect to your custom error page within the Application error event  If you choose the latter  you want to make sure you use the Server Transfer method

User · Answer

Looking more closely at my web config set up  one of the comments in this post is very helpful     in asp net 3 5 sp1 there is a new parameter redirectMode   So we can amend customErrors to add this parameter    lt customErrors mode  RemoteOnly  defaultRedirect    errors GeneralError aspx  redirectMode  ResponseRewrite    gt    the ResponseRewrite mode allows us to load the   Error Page   without redirecting the browser  so the URL stays the same  and importantly for me  exception information is not lost

User · Answer

A combination of what NailItDown and Victor said  The preferred easiest way is to use your Global Asax to store the error and then redirect to your custom error page    Global asax       void Application Error object sender  EventArgs e            Code that runs when an unhandled error occurs     Exception ex   Server GetLastError        Application  TheException     ex    store the error for later     Server ClearError      clear the error so we can continue onwards     Response Redirect    myErrorPage aspx      direct user to error page     In addition  you need to set up your web config      lt system web gt       lt customErrors mode  RemoteOnly  defaultRedirect    myErrorPage aspx  gt       lt  customErrors gt     lt  system web gt    And finally  do whatever you need to with the exception you ve stored in your error page   protected void Page Load object sender  EventArgs e                do stuff           we caught an exception in our Global asax  do stuff with it      Exception caughtException    Exception Application  TheException              do stuff

User · Answer

I think you have a couple of options here   you could store the last Exception in the Session and retrieve it from your custom error page  or you could just redirect to your custom error page within the Application error event  If you choose the latter  you want to make sure you use the Server Transfer method

User · Answer

Whilst there are several good answers here  I must point out that it is not good practice to display system exception messages on error pages  which is what I am assuming you want to do    You may inadvertently reveal things you do not wish to do so to malicious users   For example Sql Server exception messages are very verbose and can give the user name  password and schema information of the database when an error occurs   That information should not be displayed to an end user

User · Answer

OK  I found this post  http   msdn microsoft com en-us library aa479319 aspx  with this very illustrative diagram     source  microsoft com     in essence  to get at those exception details i need to store them myself in Global asax  for later retrieval on my custom error page    it seems the best way is to do the bulk of the work in Global asax  with the custom error pages handling helpful content rather than logic

User · Answer

I think you have a couple of options here   you could store the last Exception in the Session and retrieve it from your custom error page  or you could just redirect to your custom error page within the Application error event  If you choose the latter  you want to make sure you use the Server Transfer method

User · Answer

Try using something like Server Transfer    ErrorPage aspx    from within the Application Error   method of global asax cs  Then from within Page Load   of ErrorPage aspx cs you should be okay to do something like  Exception exception   Server GetLastError   GetBaseException     Server Transfer   seems to keep the exception hanging around

User · Answer

Looking more closely at my web config set up  one of the comments in this post is very helpful     in asp net 3 5 sp1 there is a new parameter redirectMode   So we can amend customErrors to add this parameter    lt customErrors mode  RemoteOnly  defaultRedirect    errors GeneralError aspx  redirectMode  ResponseRewrite    gt    the ResponseRewrite mode allows us to load the   Error Page   without redirecting the browser  so the URL stays the same  and importantly for me  exception information is not lost

User · Answer

Whilst there are several good answers here  I must point out that it is not good practice to display system exception messages on error pages  which is what I am assuming you want to do    You may inadvertently reveal things you do not wish to do so to malicious users   For example Sql Server exception messages are very verbose and can give the user name  password and schema information of the database when an error occurs   That information should not be displayed to an end user

User · Answer

I think you have a couple of options here   you could store the last Exception in the Session and retrieve it from your custom error page  or you could just redirect to your custom error page within the Application error event  If you choose the latter  you want to make sure you use the Server Transfer method

User · Answer

Here is my solution    In Global aspx   void Application Error object sender  EventArgs e                   Code that runs when an unhandled error occurs            direct user to error page          Server Transfer    ErrorPages Oops aspx             In Oops aspx   protected void Page Load object sender  EventArgs e                if   IsPostBack              LoadError Server GetLastError                 protected void LoadError Exception objError                if  objError    null                        StringBuilder lasterror   new StringBuilder                 if  objError Message    null                                lasterror AppendLine  Message                     lasterror AppendLine objError Message                   lasterror AppendLine                               if  objError InnerException    null                                lasterror AppendLine  InnerException                     lasterror AppendLine objError InnerException ToString                     lasterror AppendLine                               if  objError Source    null                                lasterror AppendLine  Source                     lasterror AppendLine objError Source                   lasterror AppendLine                               if  objError StackTrace    null                                lasterror AppendLine  StackTrace                     lasterror AppendLine objError StackTrace                   lasterror AppendLine                               ViewState Add  LastError   lasterror ToString                         protected void btnReportError Click object sender  EventArgs e                SendEmail               public void SendEmail                 try                       MailMessage msg   new MailMessage  webteam    webteam                StringBuilder body   new StringBuilder                 body AppendLine  An unexcepted error has occurred                 body AppendLine                 body AppendLine ViewState  LastError   ToString                  msg Subject    Error               msg Body   body ToString                msg IsBodyHtml   false               SmtpClient smtp   new SmtpClient  exchangeserver                smtp Send msg                      catch  Exception ex                        lblException Text   ex Message

User · Answer

OK  I found this post  http   msdn microsoft com en-us library aa479319 aspx  with this very illustrative diagram     source  microsoft com     in essence  to get at those exception details i need to store them myself in Global asax  for later retrieval on my custom error page    it seems the best way is to do the bulk of the work in Global asax  with the custom error pages handling helpful content rather than logic

User · Answer

OK  I found this post  http   msdn microsoft com en-us library aa479319 aspx  with this very illustrative diagram     source  microsoft com     in essence  to get at those exception details i need to store them myself in Global asax  for later retrieval on my custom error page    it seems the best way is to do the bulk of the work in Global asax  with the custom error pages handling helpful content rather than logic

User · Answer

It worked for me  in MVC 5   in   Global asax  void Application Error object sender  EventArgs e        FTools LogException        Response Redirect   Error           in   Controllers Create ErrorController cs  using System Web Mvc   namespace MVC WebApp Controllers       public class ErrorController   Controller                  GET  Error         public ActionResult Index                         return View  Error                           in   Models Create FunctionTools cs  using System  using System Web   namespace MVC WebApp Models       public static class FTools               private static string  error          private static bool  isError           public static string GetLastError                       get                               string cashe    error                  HttpContext Current Server ClearError                     error   null                   isError   false                  return cashe                                  public static bool ThereIsError   gt   isError           public static void LogException                         Exception exc   HttpContext Current Server GetLastError                if  exc    null  return              string errLog                   errLog                   DateTime Now               n               if  exc InnerException    null                                errLog     Inner Exception Type                     errLog    exc InnerException GetType       n                   errLog     Inner Exception                     errLog    exc InnerException Message     n                   errLog     Inner Source                     errLog    exc InnerException Source     n                   if  exc InnerException StackTrace    null                                        errLog      nInner Stack Trace        n                       errLog    exc InnerException StackTrace     n                                               errLog     Exception Type                 errLog    exc GetType   ToString       n               errLog     Exception      exc Message     n               errLog      nStack Trace        n               if  exc StackTrace    null                                errLog    exc StackTrace     n                              error   errLog               isError   true                         in   Views Create Folder Error and in   Views Error Create Error cshtml   using MVC WebApp Models        ViewBag Title    Error       if  FTools ThereIsError    false                if  Server GetLastError      null                        FTools LogException                        if  FTools ThereIsError    false                 lt br   gt           lt h1 gt No Problem  lt  h1 gt            else               string log   FTools GetLastError           lt div gt  Html Raw log Replace   n     lt br   gt     lt  div gt               If you enter this address localhost Error      And if an error occurs    As can be instead of displaying errors  variable  log  to be stored in the database       Source  Microsoft ASP Net

User · Answer

Try using something like Server Transfer    ErrorPage aspx    from within the Application Error   method of global asax cs  Then from within Page Load   of ErrorPage aspx cs you should be okay to do something like  Exception exception   Server GetLastError   GetBaseException     Server Transfer   seems to keep the exception hanging around

User · Answer

This related to these 2 topics below  I want get both GetHtmlErrorMessage and Session on Error page   Session is null after ResponseRewrite  Why is HttpContext Session null when redirectMode   ResponseRewrite  I tried and see solution which no need Server Transfer   or Response Redirect    First  remove ResponseRewrite in web config  Web config   lt customErrors defaultRedirect  errorHandler aspx  mode  On    gt    Then Global asax      void Application Error object sender  EventArgs e                 if Context IsCustomErrorEnabled                              Exception ex   Server GetLastError                Application  TheException     ex    store the error for later                    Then errorHandler aspx cs          protected void Page Load object sender  EventArgs e                                       string htmlErrorMessage   string Empty                   Exception ex    Exception Application  TheException                    string yourSessionValue   HttpContext Current Session  YourSessionId   ToString                       continue with ex to get htmlErrorMessage                  if ex GetHtmlErrorMessage      null                                     htmlErrorMessage   ex GetHtmlErrorMessage                                            continue your code                 For references  http   www developer com net asp article php 3299641 ServerTransfer-Vs-ResponseRedirect htm

User · Answer

This related to these 2 topics below  I want get both GetHtmlErrorMessage and Session on Error page   Session is null after ResponseRewrite  Why is HttpContext Session null when redirectMode   ResponseRewrite  I tried and see solution which no need Server Transfer   or Response Redirect    First  remove ResponseRewrite in web config  Web config   lt customErrors defaultRedirect  errorHandler aspx  mode  On    gt    Then Global asax      void Application Error object sender  EventArgs e                 if Context IsCustomErrorEnabled                              Exception ex   Server GetLastError                Application  TheException     ex    store the error for later                    Then errorHandler aspx cs          protected void Page Load object sender  EventArgs e                                       string htmlErrorMessage   string Empty                   Exception ex    Exception Application  TheException                    string yourSessionValue   HttpContext Current Session  YourSessionId   ToString                       continue with ex to get htmlErrorMessage                  if ex GetHtmlErrorMessage      null                                     htmlErrorMessage   ex GetHtmlErrorMessage                                            continue your code                 For references  http   www developer com net asp article php 3299641 ServerTransfer-Vs-ResponseRedirect htm

User · Answer

A combination of what NailItDown and Victor said  The preferred easiest way is to use your Global Asax to store the error and then redirect to your custom error page    Global asax       void Application Error object sender  EventArgs e            Code that runs when an unhandled error occurs     Exception ex   Server GetLastError        Application  TheException     ex    store the error for later     Server ClearError      clear the error so we can continue onwards     Response Redirect    myErrorPage aspx      direct user to error page     In addition  you need to set up your web config      lt system web gt       lt customErrors mode  RemoteOnly  defaultRedirect    myErrorPage aspx  gt       lt  customErrors gt     lt  system web gt    And finally  do whatever you need to with the exception you ve stored in your error page   protected void Page Load object sender  EventArgs e                do stuff           we caught an exception in our Global asax  do stuff with it      Exception caughtException    Exception Application  TheException              do stuff

User · Answer

It worked for me  in MVC 5   in   Global asax  void Application Error object sender  EventArgs e        FTools LogException        Response Redirect   Error           in   Controllers Create ErrorController cs  using System Web Mvc   namespace MVC WebApp Controllers       public class ErrorController   Controller                  GET  Error         public ActionResult Index                         return View  Error                           in   Models Create FunctionTools cs  using System  using System Web   namespace MVC WebApp Models       public static class FTools               private static string  error          private static bool  isError           public static string GetLastError                       get                               string cashe    error                  HttpContext Current Server ClearError                     error   null                   isError   false                  return cashe                                  public static bool ThereIsError   gt   isError           public static void LogException                         Exception exc   HttpContext Current Server GetLastError                if  exc    null  return              string errLog                   errLog                   DateTime Now               n               if  exc InnerException    null                                errLog     Inner Exception Type                     errLog    exc InnerException GetType       n                   errLog     Inner Exception                     errLog    exc InnerException Message     n                   errLog     Inner Source                     errLog    exc InnerException Source     n                   if  exc InnerException StackTrace    null                                        errLog      nInner Stack Trace        n                       errLog    exc InnerException StackTrace     n                                               errLog     Exception Type                 errLog    exc GetType   ToString       n               errLog     Exception      exc Message     n               errLog      nStack Trace        n               if  exc StackTrace    null                                errLog    exc StackTrace     n                              error   errLog               isError   true                         in   Views Create Folder Error and in   Views Error Create Error cshtml   using MVC WebApp Models        ViewBag Title    Error       if  FTools ThereIsError    false                if  Server GetLastError      null                        FTools LogException                        if  FTools ThereIsError    false                 lt br   gt           lt h1 gt No Problem  lt  h1 gt            else               string log   FTools GetLastError           lt div gt  Html Raw log Replace   n     lt br   gt     lt  div gt               If you enter this address localhost Error      And if an error occurs    As can be instead of displaying errors  variable  log  to be stored in the database       Source  Microsoft ASP Net

User · Answer

Here is my solution    In Global aspx   void Application Error object sender  EventArgs e                   Code that runs when an unhandled error occurs            direct user to error page          Server Transfer    ErrorPages Oops aspx             In Oops aspx   protected void Page Load object sender  EventArgs e                if   IsPostBack              LoadError Server GetLastError                 protected void LoadError Exception objError                if  objError    null                        StringBuilder lasterror   new StringBuilder                 if  objError Message    null                                lasterror AppendLine  Message                     lasterror AppendLine objError Message                   lasterror AppendLine                               if  objError InnerException    null                                lasterror AppendLine  InnerException                     lasterror AppendLine objError InnerException ToString                     lasterror AppendLine                               if  objError Source    null                                lasterror AppendLine  Source                     lasterror AppendLine objError Source                   lasterror AppendLine                               if  objError StackTrace    null                                lasterror AppendLine  StackTrace                     lasterror AppendLine objError StackTrace                   lasterror AppendLine                               ViewState Add  LastError   lasterror ToString                         protected void btnReportError Click object sender  EventArgs e                SendEmail               public void SendEmail                 try                       MailMessage msg   new MailMessage  webteam    webteam                StringBuilder body   new StringBuilder                 body AppendLine  An unexcepted error has occurred                 body AppendLine                 body AppendLine ViewState  LastError   ToString                  msg Subject    Error               msg Body   body ToString                msg IsBodyHtml   false               SmtpClient smtp   new SmtpClient  exchangeserver                smtp Send msg                      catch  Exception ex                        lblException Text   ex Message

[asp.net] ASP.NET custom error page - Server.GetLastError() is null

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