One of my on-prem customers is running Nintex Workflow on SharePoint 2016 and escalated an issue with setting a Taxonomy/Managed Metadata field value via a workflow. They experienced that the workflow would not change the value, or in some case it would but only once.
I managed to scope the issue down to the following:
- It works in SharePoint 2010 but doesn’t in SharePoint 2013, 2016, 2019 (had to spin up a VM of each for proper testing)
- It only affects Workflow Foundation/SharePoint 2010 Workflow Engine workflows (SharePoint Designer can create them, Nintex Workflow on-prem is based on this)
- For files that haven’t been given a value for the managed metadata field the workflow can set the value once. If the field has been set or cleared previously by UI, code, workflow, it will no longer accept new values via the workflow. For Office documents this may not work since background property promotion also causes the issue
So that makes it a pretty narrow scope and explains why there aren’t that many reports on this. But since not everyone is moving to the cloud at the same speed this is still be a relevant issue for some.
I’m going with SharePoint 2016, but I managed to reproduce this in 2013 and 2019 as well.
Create a document library and create a Managed Metadata field with some values and upload a document
Create a new workflow using the “SharePoint 2010 Workflow Platform” (SharePoint Designer or Nintex Workflow)
Configure the workflow to update the Managed Metadata field. This field expects the format TERMLABEL|TERMGUID (I’m using a hardcoded value)
Publish the workflow and run it on new files. For non-Office documents this should work once.
Next, change or clear the value through UI or whatever and run the same workflow again. You should see that even though the workflow has run it could change the value.
Workaround or fix?
I’ve been digging into the internals and it seems that once the managed metadata field is set or cleared, it keeps properties in the SPFile.Properties property bag that interfere with the update process. If you delete these properties and update the SPFile the workflow can update the value (again only once since the properties are added again).
Removing the properties requires an SPFile.Update() which in term creates a new version and is less than ideal.
Escalating this to PSS and hoping for a fix would probably be the right way, but since the narrow scope of the issue and since it is in older technology I have low hopes on this getting fixed soon.
In my case I wrote a Web Service that would allow for updating the Managed Metadata field value through the SharePoint Object Model. And this Web Method can be called in the workflow. It even allows for the workflow designer to specify the type of update (Update, UpdateOverwriteVersion or SystemUpdate). So although not very intuitive the workflow designer can now update Managed Metadata fields through the Web Method, and all other fields through the regular workflow action.