Different drivers have used some variation of "SafeMode" or "WriteConcern" to describe to what degree they want the results of an insert/update operation to be checked.

We are standardizing on WriteConcern across all drivers.

This requires some changes to the C# driver. The following classes will be renamed:

SafeMode => WriteConcern
SafeModeResult => WriteConcernResult
MongoSafeModeException => WriteConcernException

The old classes will be kept around for a few releases (but marked as Obsolete), and we are going to great lengths to keep the two sets of classes interoperable until such time as SafeMode is permanently removed.

In the short term this is slightly backward breaking because of the warnings introduced by marking things as Obsolete, as well as by minor behavior differences resulting from the changes. In the long term this is backward breaking because the classes/properties/methods with SafeMode in the name will eventually be removed.