如何將以下 SQL 查詢重寫為 LINQ 查詢？

Question

我想在 LINQ 中重寫以下 SQL 查詢。 但我的問題是我不知道如何使用 LINQ LEFT JOIN 編寫 AND (&&) 運算符（看看我的第二個左連接）。

SELECT      emp.EmployeeId,
            dsg.Name,
            pob.CompanyContribution,
            pob.EmployeeContribution,
            pob.OpeningIncome

FROM        HrmEmployees AS emp
LEFT JOIN   HrmDesignations AS dsg ON emp.HrmDesignationId=dsg.Id
LEFT JOIN   PfmOpeningBalance AS pob ON emp.Id=pob.HrmEmployeeId AND pob.CmnCalendarYearId=2
WHERE       emp.Id=6

我嘗試了以下一種。 但是得到編譯錯誤-

from emp in dbContext.EmployeeList
                        join dsg in dbContext.hrmDesig on emp.HrmDesignationId equals dsg.Id into DSGLeftJoin
                        from dsglj in DSGLeftJoin.DefaultIfEmpty()
                        join pob in dbContext.PfOpeningBalances on emp.Id equals pob.HrmEmployeeId into POBLeftJoin
                        from poblj in POBLeftJoin.DefaultIfEmpty() && poblj.CmnCalendarYearId == clndrId
                        where emp.Id==empId
                        select new
                        {
                            empIdr = emp.Id,
                            EmployeeId = emp.EmployeeId,
                            EmployeeName = emp.Name,
                            Designation = dsglj.Name,
                            OpeningIncome = poblj.OpeningIncome,
                            EmployeeContribution = poblj.EmployeeContribution,
                            CompanyContribution = poblj.CompanyContribution
                        }

Answer 1

嘗試這個。

 (from emp in HrmEmployees
  join dsg in HrmDesignations 
  on  emp.HrmDesignationId equals dsg.Id
  join pob in PfmOpeningBalance 
  on emp.Id equals pob.HrmEmployeeId AND pob.CmnCalendarYearId equals 2
  into eGroup
  from emps in eGroup.DefaultIfEmpty()
  emp.Id=6
  select new
    {
        EmployeeId =emp.EmployeeId,
        Name=dsg.Name,
        CompanyContribution=pob.CompanyContribution,
        EmployeeContribution=pob.EmployeeContribution,
        OpeningIncome=pob.OpeningIncome
    }).ToList();

Answer 2

好的，你可以這樣試試；

from emp in dbContext.EmployeeList
join dsg in dbContext.hrmDesig on emp.HrmDesignationId=dsg.Id
join pob in dbContext.PfOpeningBalanceson new {emp.Id, jp=pob.CmnCalendarYearId} equals new {pob.HrmEmployeeId, jp=2}
where emp.Id=6
select new {emp.EmployeeId,
            dsg.Name,
            pob.CompanyContribution,
            pob.EmployeeContribution,
            pob.OpeningIncome};

或者像這樣；

from emp in dbContext.EmployeeList.Where(e=>e.Id.Equals(6))
join dsg in dbContext.hrmDesig on emp.HrmDesignationId=dsg.Id
join pob in dbContext.PfOpeningBalanceson.Where(x=>x.CmnCalendarYearId.Equals(2)) on emp.Id equals pob.HrmEmployeeId
select new {emp.EmployeeId,
            dsg.Name,
            pob.CompanyContribution,
            pob.EmployeeContribution,
            pob.OpeningIncome};