Function MongoCollection.estimatedDocumentCount
Returns the count of all documents in a collection or view.
ulong estimatedDocumentCount
(
EstimatedDocumentCountOptions options = EstimatedDocumentCountOptions(Nullable(DontCallDestructorT(), true))
);
Throws Exception if a DB communication error occurred.
See Also
https://www.mongodb.com/docs/manual/reference/method/db.collection.estimatedDocumentCount/