Breaking Changes

Backwards compatibility with driver version 2.7.0–2.16.x

Driver versions 2.13.0 to 2.15.X changed EstimatedDocumentCount to use the $collStats aggregation stage instead of the count command. This unintentionally broke estimated document counts on views. 2.16.0 and later switched back to using the count command. Unfortunately MongoDB 5.0.0-5.0.8 do not include the count command in Stable API v1. If you are using the Stable API with EstimatedDocumentCount, you must upgrade to server version 5.0.9+ or set strict: false when configuring ServerApi to avoid encountering errors.

Starting from 2.15.0, feature detection is implemented through maxWireVersion instead of buildInfo. This should have no user-visible impact.

Driver version 2.14.0 and later only supports MongoDB 3.6+. It cannot connect to clusters running earlier versions of MongoDB. If you need to connect to an older cluster, please use driver version 2.13.x or earlier.

Starting in 2.11.0, BsonSerializer.Serialize will throw an InvalidOperationException when attempting to serialize an array at the root of a BSON document. Prior versions would allow this invalid operation. See and for more details.