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HomeHomeDNN Open Source...DNN Open Source...Module ForumsModule ForumsUsers OnlineUsers OnlineObject reference not set to an instance of an object - TrackAuthenticatedUserObject reference not set to an instance of an object - TrackAuthenticatedUser
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1/6/2006 8:29 PM
 
James Webster

www.mhs87.com
Joined: 12/30/2005
Posts: 63

I'm seeing the following exception quite often.  It happens on all my pages, not just the page the module is on.

System: DNN 4.00.2, UsersOnline 3.01.00

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Entities.Users.UserOnlineController.TrackAuthenticatedUser(HttpContext context) +196
   DotNetNuke.Entities.Users.UserOnlineController.TrackUsers() +95
   DotNetNuke.HttpModules.UsersOnlineModule.OnAuthorizeRequest(Object s, EventArgs e) +131
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64
 
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1/14/2006 10:12 PM
 
James Webster

www.mhs87.com
Joined: 12/30/2005
Posts: 63

Finally got my debug environment up.  This is happening in UserOnlineController.vb line 125.  In this case the code is checking if a member of the userList is null, but the userList itself is null (and never checked).

If (userList(objUserInfo.UserID.ToString()) Is Nothing) Then

The only solution for this that I see is a check for userList Is Nothing after its created, and if so, return.  I'm quite sure how it would get in this state unless the DataCache expired?!?!?

System.NullReferenceException was unhandled by user code
  Message="Object reference not set to an instance of an object."
  Source="DotNetNuke"
  StackTrace:
       at DotNetNuke.Entities.Users.UserOnlineController.TrackAuthenticatedUser(HttpContext context) in C:\Downloads\DotNetNuke_4.0.2_Source\Library\Components\Users\UserOnlineController.vb:line 125
       at DotNetNuke.Entities.Users.UserOnlineController.TrackUsers() in C:\Downloads\DotNetNuke_4.0.2_Source\Library\Components\Users\UserOnlineController.vb:line 81
       at DotNetNuke.HttpModules.UsersOnlineModule.OnAuthorizeRequest(Object s, EventArgs e) in C:\Downloads\DotNetNuke_4.0.2_Source\Library\HttpModules\UsersOnline\UsersOnlineModule.vb:line 64
       at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
       at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
 
New Post
1/22/2006 3:55 AM
 
James Webster

www.mhs87.com
Joined: 12/30/2005
Posts: 63
 
New Post
1/25/2006 9:07 AM
 
chris grimes

Joined: 1/10/2006
Posts: 6

james3838 wrote
Solution is on this thread: http://www.dotnetnuke.com/Community/ForumsDotNetNuke/tabid/795/forumid/108/threadid/14097/scope/posts/Default.aspx

James, it appears in the above thread that offered solution is to find the following 8 files:

Domain.vb
Configuration.vb
XMLLoggingProvider.vb
RewriterConfiguration.vb
ClientAPI.vb
UserOnlineController.vb
Localization.vb
SiteLogController.vb

and find the pattern:

If (DataCache.GetCache("object") Is Nothing)
   Dim obj = (... code for loading config from files ...)
   DataCache.SetCache("object", obj)
End If
Return DataCache.GetCache("object")

and replace it with this pattern:

Dim obj = DataCache.GetCache("object")
If obj Is Nothing
   obj = (... code for loading config from files ...)
   DataCache.SetCache("object", obj)
End If
Return obj

Is that right? And if so, for those of us who are users and not developers, will there be a new release with a fix for this bug soon?

Thanks,

Chris

 
New Post
1/26/2006 12:11 AM
 
James Webster

www.mhs87.com
Joined: 12/30/2005
Posts: 63

I'm actually just an end user myself that happens to code... 

I entered the bug into the bug tracker, but I don't know the schedule for fixing these issue.  Before I get my development environment up and running I had to disable that functionality.  Another work around may be to set the Host Site settings performance settings to Heavy Caching.  I didn't test that but noted that caused a different code path to be followed in the cache code itself.

If you have a development environment, here is the code I changed:

Public Function GetUserList() As Hashtable
   Dim key As String = "OnlineUserList"
   Dim userList As Hashtable = CType(DataCache.GetCache(key), Hashtable)
   ' Do we have the Hashtable?
   '
   If (userList Is Nothing) Then
      userList = New Hashtable
      DataCache.SetCache(key, userList)
   End If
   Return userList
End Function
 
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