Entity framework 如何在linq查询中获得不同的记录

您好，我已尝试在下面的查询中获取不同的记录，但无法从下面的查询中获取不同的记录

var query = (from sr in db.StudentRequests
            join r in db.Registrations on sr.RegistrationId equals r.RegistrationId
            join cc in db.Campus on r.CampusId equals cc.CampusId
            join c in db.Classes on sr.ClassId equals c.ClassId
            from tc in db.TutorClasses.Where(t => t.ClassId == sr.ClassId).DefaultIfEmpty()
            from srt in db.StudentRequestTimings.Where(s => s.StudentRequestId == sr.StudentRequestId).DefaultIfEmpty()
            from tsr in db.TutorStudentRequests.Where(t => t.StudentRequestId == srt.StudentRequestId && t.TutorId == registrationid).DefaultIfEmpty()
            where tc.RegistrationId == registrationid
            select new
            {
                StudentRequestId = sr.StudentRequestId,
                RegistrationId = sr.RegistrationId,
                Location = sr.Location,
                PaymentMethod = sr.PaymentMethod,
                CreatedOn = sr.CreatedOn,
                ClassName = c.ClassName,
                CampusName = cc.CampusName,
                StatusId = tsr.StatusId == null ? 1 : tsr.StatusId,
                Time = db.StudentRequestTimings.Where(p => p.StudentRequestId == sr.StudentRequestId)
                        .Select(p => p.FromTime.ToString().Replace("AM", "").Replace("PM", "") + "-" + p.ToTime)
            }).Distinct().ToList().ToPagedList(page ?? 1, 3);

但我也有错误

“Distinct”操作无法应用于集合 指定参数的结果类型。\r\n参数名称：参数

因此我从上面的查询中删除了.Distinct（），并在该代码下面编写了代码作为

 query = query.Distinct().ToList();

但仍然出现了重复记录

所以我尝试了按子句分组以获得清晰的记录，但在那里我也面临着这个问题。请查看下面的代码

query = query.ToList().GroupBy(x => new { x.StudentRequestId, x.StatusId, x.Location, x.RegistrationId, x.PaymentMethod, x.CreatedOn, x.ClassName, x.CampusName})
.Select(group => new
{
    StudentRequestId = group.Key.StudentRequestId,
    StatusId = group.Key.StatusId,
    Location = group.Key.Location,
    RegistrationId = group.Key.RegistrationId,                                    
    PaymentMethod = group.Key.PaymentMethod,
    CreatedOn = group.Key.CreatedOn,
    ClassName = group.Key.ClassName,
    CampusName = group.Key.CampusName,                                   
    Time1 = group.Key.Time
});

但我得到了错误的时间

如何获得不同的值？ 还请注意，我在查询中使用了ToPagedList

---

实际问题来自时间列，如果我删除该列，所有事情都会正常进行。

我在查询末尾添加了Group by子句，正如@Rajaji所建议的那样，这对我来说很有效

 var query = (from sr in db.StudentRequests
             join r in db.Registrations on sr.RegistrationId equals r.RegistrationId
             join cc in db.Campus on r.CampusId equals cc.CampusId
             join c in db.Classes on sr.ClassId equals c.ClassId
             from tc in db.TutorClasses.Where(t => t.ClassId == sr.ClassId).DefaultIfEmpty()
             from srt in db.StudentRequestTimings.Where(s => s.StudentRequestId == sr.StudentRequestId).DefaultIfEmpty()
             from tsr in db.TutorStudentRequests.Where(t => t.StudentRequestId == srt.StudentRequestId && t.TutorId == registrationid).DefaultIfEmpty()
             where tc.RegistrationId == registrationid
             select new
             {
               StudentRequestId = sr.StudentRequestId,
               RegistrationId = sr.RegistrationId,
               Location = sr.Location,
               PaymentMethod = sr.PaymentMethod,
               CreatedOn = sr.CreatedOn,
               ClassName = c.ClassName,
               CampusName = cc.CampusName,
               StatusId = tsr.StatusId == null ? 1 : tsr.StatusId,
               Time = db.StudentRequestTimings.Where(p => p.StudentRequestId == sr.StudentRequestId).Select(p => p.FromTime.ToString().Replace("AM", "").Replace("PM", "") + "-" + p.ToTime)
               }).ToList().GroupBy(p => new { p.StudentRequestId }).Select(g => g.First()).ToList();

---

而不是使用…GroupBy（）.Select（g=>g.First（））.ToList（）@为我工作的Rajaji，谢谢。