是這樣的我想做一個查詢功能，查詢這個日期到這個日期裡的所有資料，格式是用
民國，例如我想查107/11/11~107/12/10間的資料，可是我想查12/10號的資料時
12月/10號的資料就直接消失，請問這是什麼原因?

controller:

 public ActionResult HDNurseRecordList(HDNurseRecordQueryViewModel model)
        {
            if (!String.IsNullOrWhiteSpace(model.EndDateString))
            {
                model.EndDate = DateHelper.ToDate(model.EndDateString);
            }
            if (!String.IsNullOrWhiteSpace(model.StartDateString))
            {
                model.StartDate = DateHelper.ToDate(model.StartDateString);
            }

            PatInfoSession pat = SessionPatInfo();
            HDNurseRecordService hdn = new HDNurseRecordService();

            model.HDNurseRecords = hdn.FindNRecId(pat.PatGuid, model.StartDate, model.EndDate);
            if (model.HDNurseRecords == null) model.HDNurseRecords = new List<HDNurseRecordListDto>();
            
            model.StartDateString = DateHelper.ToDate(model.StartDate);
            model.EndDateString = DateHelper.ToDate(model.EndDate);

            return View(model);
        }

ToDate方法:

 public static DateTime ToDate(string dt)
        {
            if (String.IsNullOrWhiteSpace(dt)) return new DateTime(1900, 1, 1);

            string[] dts = dt.Split('/');
            if (dts.Length < 3) return new DateTime(1900, 1, 1);

            int year = Int32.Parse(dts[0]) + 1911;
            int mon = Int32.Parse(dts[1]);
            int day = Int32.Parse(dts[2]);

            return new DateTime(year, mon, day, 0, 0, 0);
        }
                

 public static string ToDate(DateTime dt)
        {       
            if (IsDefaultDate(dt)) return "";
            if (dt == null || dt.Year == 1) return "";
            string dateStr = dt.ToString("/MM/dd");
            string year = (dt.Year - 1911).ToString();
            return year + dateStr;
            //return dt.ToString("yyyy/MM/dd");
        }

service層:

 public List<HDNurseRecordListDto> FindNRecId(string pat_guid, DateTime StartDate, DateTime EndDate)
        {
            if (String.IsNullOrWhiteSpace(pat_guid)) return null; 
            List<HDNurseRecordListDto> dtos = (from x in _repo.HD_NURSE_RECORD
                         where
                            pat_guid == x.PAT_GUID && x.RECORD_DATETIME >= StartDate && x.RECORD_DATETIME <= EndDate
                         select new HDNurseRecordListDto
                         {
                             RECORD_DATETIME = x.RECORD_DATETIME,
                             NURSE_EMP_ID = x.NURSE_EMP_ID,
                             CID = x.CID,
                             CONTENT = x.CONTENT,
                             CRE_UID = x.CRE_UID,
                             GUID = x.GUID,
                             MOD_UID = x.MOD_UID,
                             PAT_GUID = x.PAT_GUID
                         }).OrderByDescending(x=>x.RECORD_DATETIME).ToList<HDNurseRecordListDto>();
           foreach (HDNurseRecordListDto dto in dtos)
           {
              dto.Name = _repo.EMPLOYEE.Where(x => x.CID == dto.CID && x.EMP_ID == dto.NURSE_EMP_ID).FirstOrDefault<EMPLOYEE>().EMP_NAME;
           }
          return dtos;
        }

view model裡我是給這樣的值

 StartDate = DateTime.Now.AddDays(-30);
 EndDate = DateTime.Now;

還請各位告訴我原因及解法，謝謝