I have code that used to work and has stopped. The code defines a member of a base class as the "ID" via the usual pattern.

BsonClassMap.RegisterClassMap<Message>(cm =>

{ cm.AutoMap(); cm.SetIdMember(cm.GetMemberMap(c => c.UniqueId)); }

);

where UniqueID is a GUID.

I Dropped the collection containing this type ( and its decendents) and reinstered an instance of a derived class.

The database after the insert has an _id with an ObjectId in it !! A subsequent deserialize fails trying to make objectid into guid.

Any thoughts on what I could have done to break this.