Fix for Silverlight Error When Trying to Show Jobs and Tasks in Manage Computers

After this topic came up 2 times already at the same customer I need to write it down somewhere to remind myself and why not share it with the community.

Problem Description

The silverlight console starts showing errors instead of loading the jobs and tasks details for a selected computer. Other Computer might still show the list of jobs and task run and running as usual.

Silverlight gives an error message about some unknown exception during loading the Taskhistory.

If you use the Resource Manager and check Jobs and Tasks Summary there you will still see all the Tasks run.

Cause

The silverlight module doesn't really like NULL values. In this case it was older deleted Tasks. When silverlight tries to get details for the Task Instance it will be presented with NULL for some of the Taskinstances of the computer. If you check in the database you will also find those Instance orphans.

Solution

Run the following SQL query to find all the taskinstances that don't have any taskversion or task/job item attached anymore. After a backup of the DB you could change the "select * " to "delete " and get rid of the orphaned taskinstances. If I missed something please feel free to comment.

select * from taskinstances where taskinstances.TaskInstanceGuid in(select ti.TaskInstanceGuid from taskinstances ti

left join itemversions iv

on ti.TaskVersionguid = iv.Versionguid

left join item i

on iv.Itemguid = i.guid

join Taskinstanceresults tir

on tir.TaskInstanceGuid = ti.TaskInstanceGuid

where i.Name is NULL and i.Guid is NULL and iv.ItemGuid is NULL)