Mongodb在CSharp里实现Aggregate实例

/// <summary>    /// 返回UI消息树    /// </summary>    /// <returns></returns>    public static string GetMongoLog(DateTime? fromDate, DateTime? toDate, int page = 1)    {      string from = DateTime.Now.Date.ToString("yyyy-MM-dd");      string to = DateTime.Now.Date.AddDays(1).ToString("yyyy-MM-dd");      if (fromDate.HasValue)      {        from = fromDate.Value.ToString("yyyy-MM-dd");      }      if (toDate.HasValue)      {        to = toDate.Value.ToString("yyyy-MM-dd");      }      var stages = new List<IPipelineStageDefinition>();      stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>("{$match:{AddTime:{$gt:ISODate('" + from + "'),$lt:ISODate('" + to + "')}}}"));      stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>("{$group:{_id: /"$RootId/", count: {$sum: 1}}}"));      stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>("{$skip:" + page * 5 + "}"));      stages.Add(new JsonPipelineStageDefinition<BsonDocument, BsonDocument>("{$limit:5}"));      var pipeline = new PipelineStagePipelineDefinition<BsonDocument, BsonDocument>(stages);      var result = NoSql.MongodbManager<LoggerContext>.Collection.Aggregate(pipeline);      StringBuilder str = new StringBuilder();      str.Append("<ol class='treeMsg'>");      foreach (var item in result.ToList())      {        var timer = new List<DateTime>();        var old = NoSql.MongodbManager<LoggerContext>.Instance.Find(i => i.RootId == item.Values.ToArray()[0].ToString() && i.ParentId == null).FirstOrDefault();        timer.Add(old.AddTime);        str.Append("<li style='margin:5px;border:1px dashed #aaa'>");        str.AppendFormat("<span style='color:red;'>{0}</span><span style='color:green'>{1}</span><span>{2}</span>"          , old.Url          , old.MessageBody          , old.AddTime);        MsgTree(str, old.ChildId, timer);        str.AppendFormat("<p><b><em>本次请求用时{0}毫秒（{1}秒）<em></b></p>"          , (timer.Max() - timer.Min()).TotalMilliseconds          , (timer.Max() - timer.Min()).TotalSeconds);        str.Append("</li>");      }      str.Append("</ol>");      return str.ToString();    }