I am trying to create a document set through the CSOM API and my solution was working for several days and then suddenly stopped working. None of my code changed, and the admin of the sharepoint server I am communicating with insists that nothing has changed there either. The line that fails is the "DocumentSet.Create" call. Code below (I've omitted my error checking and exception handling for clarity/brevity):
// Retrieving parent folder where I also ensure it's not null
Folder parentFolder = GetParentFolder(context);
var contentType = context.Web.ContentTypes.FirstOrDefault( ct => ct.Name == "Some document type");
var response = DocumentSet.Create( context, parentFolder, "Deal #1, contentType.Id );
context.ExecuteQuery();
The response is always empty/null, and when I capture the exception that gets thrown it simply says "Unknown error". Again, this solution went from working to not-working without any code changes.
Is there anything that could have changed on the Sharepoint Server that could have caused this? I can still perform other operations (reading/writing/deleting documents), so I'm confident my "context" isn't the problem.