MongoDB查询数据效率慢

[SDHU]

库中一共有四个实体，通过类似ef的框架关联起来，主要的其中3个实体TStudy，TSeries，TPatient如下：
这是TStudy

  [BsonId]
        public string InstanceUID { get; set; }
        
        [BsonElement("StudyID")]
        public string StudyID { get; set; }

        [BsonElement("StudyDate")]
        public DateTime? StudyDate { get; set; }

        [BsonElement("StudyTime")]
        public DateTime? StudyTime { get; set; }

        [BsonElement("Modility")]
        public string Modility { get; set; }

        [BsonElement("StudyDescription")]
        public string StudyDescription { get; set; }

        [BsonElement("IsCompleted")]
        public int IsCompleted { get; set; }

        [BsonElement("Patient")]
        public TPatient Patient { get; set; }

        [BsonElement("LockedState")]
        public string LockedState { get; set; }

        [BsonElement("Series")]
        List<TSeries> _series;

这是Tseries：

  [BsonIgnore]
        public const string TBName = "tseries";

        [BsonId]
        public string InstanceUID { get; set; }

        [BsonElement("SeriesNumber")]
        public string SeriesNumber { get; set; }

        [BsonElement("SeriesType")]
        public string SeriesType { get; set; }

        [BsonElement("ImageCount")]
        public ushort ImageCount { get; set; }

        [BsonElement("SeriesDescription")]
        public string SeriesDescription { get; set; }

        [BsonElement("ProtocolName")]
        public string ProtocolName { get; set; }

        [BsonElement("BodyPartExamined")]
        public string BodyPartExamined { get; set; }

        [BsonElement("StudyInstanceUID")]
        public string StudyInstanceUID { get; set; }

        [BsonElement("LockedState")]
        public string LockedState { get; set; }

        [BsonElement("Contrast")]
        public bool? Contrast { get; set; }

        [BsonElement("IsPreview")]
        public bool? IsPreview { get; set; }

        [BsonElement("ScanSeriesUID")]
        public string ScanSeriesUID { get; set; }
        
        [BsonElement("PacsAddress")]
        public string PacsAddress { get; set; }

        [BsonElement("PacsAE")]
        public string PacsAE { get; set; }

        [BsonElement("PrinterAE")]
        public string PrinterAE { get; set; }

这是TPatient：

 [BsonIgnore]
        public const string TBName = "tpatient";

        [BsonId]
        public string StudyUID { get; set; }

        [BsonElement("AccessionNumber")]
        public string AccessionNumber { get; set; }

        [BsonElement("PatientID")]
        public string PatientID { get; set; }

        [BsonElement("PatientName")]
        public string PatientName { get; set; }

        [BsonElement("Sex")]
        public string Sex { get; set; }

        [BsonElement("Birthday")]
        public DateTime? Birthday { get; set; }

        [BsonElement("Age")]
        public string Age { get; set; }

        [BsonElement("ReferringPhysician")]
        public string ReferringPhysician { get; set; }

        [BsonElement("Operator")]
        public string Operator { get; set; }

        [BsonElement("History")]
        public string History { get; set; }

        [BsonElement("StudyDescription")]
        public string StudyDescription { get; set; }

        [BsonElement("StudyDate")]
        public DateTime? StudyDate { get; set; }

        [BsonElement("StudyTime")]
        public DateTime? StudyTime { get; set; }

        [BsonElement("Editlogs")]
        private  List<TEditlog> _editlogs { set; get; }

然后通过以下方式查询到指定时间内的所有数据：

  private IMongoCollection<TStudy> _studies => _database.GetCollection<TStudy>(TStudy.TBName);

  var fromTimeFilter = Builders<TStudy>.Filter.Gt("StudyDate", fromTime);
            var toTimeFilter = Builders<TStudy>.Filter.Lt("StudyDate", toTime);
            var searchFilter = Builders<TStudy>.Filter.And(fromTimeFilter, toTimeFilter);
            return _studies.Find(searchFilter).ToEnumerable();

上层界面获取到IEnumerable<TStudy> 类型的数据后直接绑定到datagrid，只有200组数据，但是下面的这段代码需要近两秒的时间，用mysql+Linq，从查询到显示结果花费的时间1s都不到，差距有点大，请问是我那里优化不对么？
我感觉是不是在_studies.Find(searchFilter).ToEnumerable() 返回的时候是不是mongo内部还没有真正将数据库中的数据映射到实体中， 直到数据源绑定的时候才开始映射数据，而映射的这一步又比较耗时么？

[SDHU]

耗时的代码上面忘了贴了