The Problem

After updating a DNN site from 05.01.01 to DNN 05.06.00 we received the following error.

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Object reference not set to an instance of an object.
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.Portals.PortalSettings..ctor(Int32 tabID, PortalAliasInfo objPortalAliasInfo) +49
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +2087
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +68
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

 

We found that this is a bit of a reported issue with DNN websites that have been upgraded to DNN 05.06.00. There is a bit of chatter about it here:
http://www.dotnetnuke.com/Resources/Forums/tabid/795/forumid/200/threadid/396504/scope/posts/Default.aspx

Basically the problem is that if you access a page like

http://domain.com/AboutUs/History/tabid/108/Default.aspx The site will work.

but if you access http://www.domain.com  it fails.

There is a lot of heads spinning on this one, talk about the HTTP handler and there is no doubt in our mind that much is not right with the DNN 05.06.00 release. Actually this release has probably caused us the most headaches for our modules in the last few years.

The Fix

We found the fix for this problem is easy. Set the IIS Application Pool that relates to the site’s managed pipeline to “Integrated” from “classic”.

In IIS 7

it looks a little like that.

This should fix this particular bug in a few seconds.