Hi, @alexov_inbox,
The new LINQ3 provider can be enabled through MongoClientSettings.LinqProvider. You can find a code example of how to do this in our 2.14 docs:
http://mongodb.github.io/mongo-csharp-driver/2.14/reference/driver/crud/linq3/
Please let us know if you have any questions. We look forward to your feedback on the new LINQ provider. If you encounter an issue, please file a CSHARP ticket here.
Sincerely,
James