If you get an error like this:

MongoDB.Bson.BsonSerializationException: Duplicate element name 'EntryId' in class 'LoopLib.Common.LogEntry'

It might not have nothing to do with "EntryId". It's due to a duplicate BsonElement name anywhere in the
class, not necessarily on that field.

For example, I had something like this:

[BsonId]
public Guid EntryId

[BsonElement("a")]
public int B

For people who are renaming their fields to save storage space, this will be a common mistake.