var documentSerializer = MongoDB.Bson.Serialization.BsonSerializer.SerializerRegistry.GetSerializer<LegacyOrder>();
var dd = lessQuotedFilter.Render(documentSerializer, MongoDB.Bson.Serialization.BsonSerializer.SerializerRegistry).ToString();
C# mongodb Filter BsonSerializer
原文：https://www.cnblogs.com/eoore/p/14636686.html