Symptoms
When executing the SmartObject that points to a list on a SP2013 site, then getting this error:
Cannot set Column 'Checklistenkategorie_x003a_ID' to be null. Please use DBNull instead.
Service: qateamsites_intranet_com___sites___526
Service Guid:
Severity: Error
Diagnoses
So the original issue was that you deleted a category inside a list and then re-created that category. K2 wasn't able to find the original category, so you had to make some changes in the SP List that K2 was able to "see" these items again.
Here is how you described it:
In SharePoint List "Checklistenelemente" there were items that came from a category out of a different list (Lookup Field). The testers deleted and re-created a category in that list. Now the items that referred to that category caused the problems. In the SharePoint list "Checklistenelemente", I had to refresh / update the items.
Resolution
We tried to link this to a TFS item so K2 would use the list name to detect the changes, however the issue here is we cannot simply “assume” that 2 lists are the same. In an environment I can imagine 3 sites:
https://portal.denallix.com/HR/HR/Lists/Document Approval
https://portal.denallix.com/PM/Lists/Document Approval
https://hr.denallix.com/HR/Lists/Document Approval
We simply cannot assume that either one of those are the correct lists and just deploy to that list. If we don’t show a conflict some clients might just see “all green / go for green” and hit finish and we run into a situation where some artifacts are overridden.