I am creating document sets through workflows. Edit: I just tested and I'm getting this message for manually created documents sets as well. Every new document set is showing the message:
Content types that are available to this Document Set have been added or removed.
In its welcome page. Edit: There is also a link to "update the document set". Clicking on it just refreshes the page, but the error message and the link are still there.
I have read about it, and people around the internet generally suggest three solutions:
docset_LastRefreshproperty of the document set. One guy said this on MSDN years ago and many people have been parroting it ever since. Problem is, it just doesn't work. The property is changed but other than that nothing happens.
Provisioning the document set. Can't be done via CAML for obvious reasons, and when I try calling the
provisionmethod in an event receiver, I get the exception below. Since I'm coding in the same machine where the server is, and I have the assembly, I'm assuming this is because the solution is sandboxed.
Could not load type 'Microsoft.SharePoint.SPLongOperationState' from assembly 'Microsoft.SharePoint, Version=14.900.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'.
Creating the document sets from a Visual Studio workflow instead of a SPD one. Unfortunately, I have to deliver the solution as a sandbox one, and that excludes VS workflows.