C# 这个LINQ查询不正确吗？

所以我现在做的是一个查询，在本例中，通过员工2015年某一年的ID获取员工的缺勤情况

这是DB模型，这些是类：

[Serializable] 
public class Absence
{
    public Int32 IDAbsence;
    public Int32 IDEmployee;
    public Int32 Period;
    public DateTime BeginDate;
    public DateTime? EndDate;
    public AbsenceType AbsenceType;
    public AbsenceStatus AbsenceStatus;
    public List<Justification> Justifications;
    public List<Notification> Notifications;

    public Absence() { }

    public Absence(Int32 IDAbsence, Int32 IDEmployee, Int32 Period, DateTime BeginDate, DateTime? EndDate, AbsenceType AbsenceType, AbsenceStatus AbsenceStatus, List<Justification> Justifications, List<Notification> Notifications)
    {
        this.IDAbsence = IDAbsence;
        this.IDEmployee = IDEmployee;
        this.Period = Period;
        this.BeginDate = BeginDate;
        this.EndDate = EndDate;
        this.AbsenceType = AbsenceType;
        this.AbsenceStatus = AbsenceStatus;
        this.Justifications = Justifications;
        this.Notifications = Notifications;
    }
    }

[Serializable] 
    public class TimePeriod
    {
        public Int32 IDTimePeriod;
        public DateTime StartTime;
        public DateTime EndTime;

        public TimePeriod() { }

        public TimePeriod(Int32 IDTimePeriod, DateTime StartTime, DateTime EndTime)
        {
            this.IDTimePeriod = IDTimePeriod;
            this.StartTime = StartTime;
            this.EndTime = EndTime;
        }
    }

这就是错误：

对象引用未设置为对象的实例

奇怪的是，因为我在DB中查到了该员工2015年的缺勤记录，以及相应的时间段。没有任何情况下Period未找到相应的IDTimePeriod

我错过了什么

试试看：

public static List<Tuple<Absence,TimePeriod>> GetAbsencesByEmployeeIDAndYear(Int32 employeeID, Int32 year) {

    List<Tuple<Absence,TimePeriod>> absences = dataContext.Absences.Join(dataContext.TimePeriods,
     abs => abs.Period,
     tps => tps.IDTimePeriod,
     (abs, tps) => new { abs, tps})
     .Where(x => x.abs.Employee.IDEmployee == employeeID && x.tps.StartTime.Year == year)
    .Select(t => new Tuple<Absence,TimePeriod>(t.abs, t.tps))
    .ToList();

    return absences;
}

---

如果此查询正确，您将获得预期的输出是否确实初始化了dataContext？Employee.IdeEmployee不应该只是IdeEmployee吗？请尝试将wherebStps=>abstps.Item1.Employee.IdeEmployee==employeeID&&abstps.Item2.StartTime.Year==Year替换为wherebStps=>abstps.Item1！=null&&absps.Item1.Employee！=null&&absps.Item1.Employee.ideemployee==employeeID&&absps.Item2！=null&&absps.Item2.StartTime.Year==yearYes是的，我初始化了dataContext。。。Artem说EmployeeID不应该在那里，我删除了它，因为Employee类有一个缺勤列表，所以你必须在获取员工ID之前获取该员工。Ako我仍然得到错误…LINQ to Entities中只支持无参数构造函数和初始值设定项。我成功地获取了它。。。我必须在to列表和select and expect之间切换，以获得一个IEnumerable

public static List<Tuple<Absence,TimePeriod>> GetAbsencesByEmployeeIDAndYear(Int32 employeeID, Int32 year) {

    List<Tuple<Absence,TimePeriod>> absences = dataContext.Absences.Join(dataContext.TimePeriods,
     abs => abs.Period,
     tps => tps.IDTimePeriod,
     (abs, tps) => new { abs, tps})
     .Where(x => x.abs.Employee.IDEmployee == employeeID && x.tps.StartTime.Year == year)
    .Select(t => new Tuple<Absence,TimePeriod>(t.abs, t.tps))
    .ToList();

    return absences;
}