Question

我使用ASP MVC，我有这个LINQ让员工DTR：

 IEnumerable<DatatablesViewModel> viewmodel = 
     (from a in db.tHREmployees
      join b in db.tTADTRs on a.EmpID equals b.EmpID
      join c in db.tHRJobGrades on a.JobGrdID equals c.JobGrdID
      join d in db.tTAShifts on b.ShftID equals d.ShftID
      join e in db.tTADays on b.DayID equals e.DayID
      where (b.LogDt >= PeriodDates.FromDt && b.LogDt <= PeriodDates.ToDt)
      select new DatatablesViewModel
      {
          EmpID = a.EmpID,
          Name = a.LastNm + ", " + a.FirstNm + ", " + a.MiddleNm,
          JobGradeDesc = c.JobGrdDesc,
          ShftNm = d.ShftNm,
          DayType = e.DayNm,
          LogDT = b.LogDt,
          LogIn = b.LogIn,
          LogOut = b.LogOut,
          Absent = b.AbsDay,
          Work = b.WorkHr,
          Late = b.LateHr,
          Overtime = b.OTHr,
          Undertime = b.OTHr,
          Nightdiff = b.NDHr,
          NightPrem = b.NPHr,
          ApprovedOT = b.AppOT,
          ApprovedOB = b.AppOB,
          ApprovedCoa = b.AppCOA,
          ApprovedCs = b.AppCS,
          Exception = b.ExcptStatus
      }).OrderBy(x => x.EmpID);

在我看来，我的下拉菜单的员工姓名带有'ALL'选项。我想在上面代码中的'where'里面添加一个条件，如：

if(parameter.selectedEmp != "ALL"){
Where(x => x.EmpID == param.CustomParam_EmpID) <-- add this filter

}

我想只选择查询中需要的内容以避免延迟。

Answer 1

您无需直接在Where子句中添加它。只有在您开始遍历集合时，才会评估IEnumerable和您的LINQ查询。你可以简单地做这样的事情：

var relevantVMObjects = 
 (from a in db.tHREmployees
  join b in db.tTADTRs on a.EmpID equals b.EmpID
  join c in db.tHRJobGrades on a.JobGrdID equals c.JobGrdID
  join d in db.tTAShifts on b.ShftID equals d.ShftID
  join e in db.tTADays on b.DayID equals e.DayID
  where (b.LogDt >= PeriodDates.FromDt && b.LogDt <= PeriodDates.ToDt)
  select new DatatablesViewModel
  {
      EmpID = a.EmpID,
      Name = a.LastNm + ", " + a.FirstNm + ", " + a.MiddleNm,
      JobGradeDesc = c.JobGrdDesc,
      ShftNm = d.ShftNm,
      DayType = e.DayNm,
      LogDT = b.LogDt,
      LogIn = b.LogIn,
      LogOut = b.LogOut,
      Absent = b.AbsDay,
      Work = b.WorkHr,
      Late = b.LateHr,
      Overtime = b.OTHr,
      Undertime = b.OTHr,
      Nightdiff = b.NDHr,
      NightPrem = b.NPHr,
      ApprovedOT = b.AppOT,
      ApprovedOB = b.AppOB,
      ApprovedCoa = b.AppCOA,
      ApprovedCs = b.AppCS,
      Exception = b.ExcptStatus
  }).OrderBy(x => x.EmpID);

 if(parameter.selectedEmp != "ALL")
      relevantVMObjects = relevantVMObjects.Where(x => x.EmpID == param.CustomParam_EmpID);
 IEnumerable<DatatablesViewModel> viewmodel = relevantVMObjects;

Answer 2

您可以通过OR条件

执行此操作

string selectedEmp=parameter.selectedEmp;
IEnumerable<DatatablesViewModel> viewmodel = 
     (from a in db.tHREmployees
      join b in db.tTADTRs on a.EmpID equals b.EmpID
      join c in db.tHRJobGrades on a.JobGrdID equals c.JobGrdID
      join d in db.tTAShifts on b.ShftID equals d.ShftID
      join e in db.tTADays on b.DayID equals e.DayID
      where (b.LogDt >= PeriodDates.FromDt && b.LogDt <= PeriodDates.ToDt) &&
      (selectedEmp != "ALL" || a.EmpID == param.CustomParam_EmpID)
 select new DatatablesViewModel
      {
           ...
      }

LINQ条件里面要过滤哪里

2 个答案: