Wednesday, August 13, 2008

Programatically removing an HttpModule from SharePoint Web.config (2)

In one of my previous posts (that you can find here) I described how I managed to add a HttpModule tag to the web.config. The issue still remaining was the removal of that tag from the web.config, that I needed to do in the uninstallation process (in my case feature deactivating). At that time I used a remove tag. 

Although web.config file sees no problem in duplicate add tags, the same thing does NOT happen with the remove tags. If two or more remove tags of the same module are present in the web.config file, an error is generated - so down the drain goes our solution if two or more install-uninstall sequences occur on the same web application.

What is the solution to this problem? I found it in one of Andrew Connell's books - "Professional SharePoint 2007 Web Content Management Development" (find it in my Books sidebar). It is a fairly simple solution: at Http Module installation in a SharePoint site you add a property to the site to signal that the Http Module should be applied there. In the Http Module code behind you check if that property exists before letting the Http Module do what it is meant to do. At unistallation you remove the property, or make it null. And Voila! - although the tag in the web.config stands, the module will not act on sites unless they have the property it is looking for.

 
Posted by Madalina at 14:12:14 | Permanent Link | Comments (0) |

Tuesday, June 17, 2008

Programatically add (and remove) an HttpModule to SharePoint Web.config

Sometimes you need to use an HttpHandler or HttpModule in a SharePoint application - I am using one to handle the requests to the system pages and to replace the application.master on them with my own master. To install this module I need to register the dll in the GAC and to add a HttpModule declaration in the web.config.

To modify the web.config programatically in SharePoint you can use the SPWebConfigModification class. There are many examples on the net about using this class, and the one I started with is this one. Unfortunately, this example, along with all the others on the subject are healing with adding HttpHandler elements, while I needed to play with an HttpModule element. The example does apply to me for adding an element, but the issue arises when I need to remove it.

The SPWebConfigModification class has a Name property. This property should be set to the relative XPath to the modification and maps to the Path attribute of an HttpHandler element. The property is used to locate the element when you need to remove it. Unfortunately, the HttpModule element does not have the Path attribute. So no matter how I tried it, I could not remove the element from the web.config.

The solution came while I was reading a different post about web.config inheritance: the tag. If you want to remove the HttpModule element, add a tag to the web.config.

Posted by Madalina at 11:34:33 | Permanent Link | Comments (2) |