I have found a rather unsatisfactory answer to my crash from a few days ago.
You have to add the package Microsoft.Azure.Graphs 0.3.1-preview first, which brings in Microsoft.Azure.DocumentDB 1.14.0 and NETStandard.Library 1.6.1 (which in turns pulls in about 70 other packages). I was adding the first two packages in reverse order and using the highest DocumentDb 2.0 which must have revealed an internal discrepancy via a method not found. I get 25 package update offers, which I'll ignore for now or it will surely all break again. By using the lower version default packages my Cosmos DB Graph queries are now working. *Greg K*
