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# Tuesday, 27 October 2009
Tuesday, 27 October 2009 20:06:12 (GMT Standard Time, UTC+00:00) ( Umbraco )

This Blog is not active anymore, further posts will be available on my company website. Read new posts here

A few weeks back I had this  issue when deploying a site. I needed to modify a documenttype to add a few properties and after a few minutes an error was raised and the only thing I could see when I deleted the property and saved the documenttype again, or opened a document based on that document type was the following error message (thanks Dan for the picture). 

error-delete (3)

Did I make a backup? ehh no, so I needed to fix this. Okay let’s look at  the error message again. An Object reference not set error is thrown while deleting the property. Love that Umbraco is open source and I can have a look at the source code. Below you see the method that is responsible for deleting the property from the documenttype.

   1:          public void delete()
   2:          {
   3:              // flush cache
   4:              FlushCache();
   6:              // Delete all properties of propertytype
   7:              foreach(Content c in Content.getContentOfContentType(new ContentType(_contenttypeid)))
   8:              {
   9:                  c.getProperty(this).delete();
  10:              }
  11:              // Delete PropertyType ..
  12:              SqlHelper.ExecuteNonQuery("Delete from cmsPropertyType where id = " + this.Id);
  13:              this.InvalidateCache();
  14:          }

As you might have seen there is no check for null values on the 9 (c.getProperty(this).delete();). This is what caused the error while deleting the property. I assume it's sort of the same issue when opening a document. Now that I know this I can work on a solution. As I mentioned earlier, I needed to add properties to the document type. Below you find the code I’ve used to do that.

   1:   ContentType ct = ContentType.GetByAlias("_advertiser");
   2:          foreach (PropertyType i in ct.PropertyTypes)
   3:          {
   4:              if (i.Alias == "linkToSpecial")
   5:              {
   6:                  // Delete all properties of propertytype
   7:                  foreach (umbraco.cms.businesslogic.Content c in umbraco.cms.businesslogic.Content.getContentOfContentType(ct))
   8:                  {
   9:                      if (c.getProperty("linkToSpecial") == null)
  10:                      {
  11:                          c.addProperty(i, c.Version);
  12:                          c.Save();
  13:                      }
  14:                  }
  15:                  //Remove comment to delete the property from the doctype
  16:                  //i.delete();
  17:                  //ct.Save();
  18:              }
  19:          }

As you can see, I’ve used a  few hard coded values. _advertiser is the alias of the document type and linkToSpecial is the alias of the property that I wanted to add on the Document type. If you want to delete the property  remove  lines 9-13 and remove the comment on line 16 and 17. You can use this code in a usercontrol and use that usercontrol as a dashboard control. Needless to say, this code comes without a warranty.

I’ve added the issue to codeplex, please vote for it!. Hope this post is a nice work around for the issue.