Currently the C# driver will not connect to a replica set when there is no primary. However, it is possible that some applications will wish to connect in read-only mode in such a scenario. Should the driver connect successfully when there is no primary (and only fail when writes are attempted)? Does this require a new connection string option to specify whether a primary is required or not? A similar scenario occurs when a primary exists when first connecting but then steps down subsequently: should the driver allow reads to continue while there is no primary?