Question

我对LINQ to SQL很新，并尝试在LINQ中编写以下查询。有人可以指导我如何在LINQ中编写它。

Select  app.ApplicationGenID, max(appHis.ApplicationStatusHistoryGenID), max  (appHis.ApplicationStatusGenID)
from Application app
join Applicant appl on app.ApplicantGenId = appl.ApplicantGenID
Left Outer Join ApplicationStatus appStatus on app.ApplicationGenID = appStatus.ApplicationGenID
Where appl.ClientID=4 and (app.IsDeleted=0 or app.IsDeleted is null)
Group By app.ApplicationGenID

Answer 1

我只是没有从您的SQL查询中看到您在哪里获得appHis表。

但是，如果您的表上有密钥，扩展方法语法中的 LinQ 应该如下所示：

  var res = _context.Applicant
                .Where(x => x.ClientID == 4 
                    && (x.Application.IsDeleted == 0 || x.Application.IsDeleted == null))
                    .GroupBy(x => x.ApplicationGenID)
                    .Select(x => new 
                    {
                        ApplicationGenID = x.Key,
                        //Not sure about next 2 lines, couse i don't know where you get appHis
                        ApplicationStatusHistoryGenID = x.Max(y => y.ApplicationStatusHistoryGenID),
                        ApplicationStatusGenID = x.Max(y => y.ApplicationStatusGenID)
                    });

Answer 2

谢谢你的帮助。这就是我最终做到的方式。把它放在这里供将来参考。

var result = (from app in context.Application
                                join appl in context.Applicant on new {ApplicantGenId = app.ApplicantGenId} equals
                                    new {ApplicantGenId = appl.ApplicantGenID}
                                join appStatus in context.ApplicationStatus on app.ApplicationGenID equals
                                    appStatus.ApplicationGenID into appStatus_join
                                from appStatus in appStatus_join.DefaultIfEmpty()
                                join refStatus in context.ref_ApplicationStatus on appStatus.ApplicationStatusGenID
                                    equals refStatus.ApplicationStatusGenID into refStatus_join
                                from refStatus in refStatus_join.DefaultIfEmpty()
                                where
                                    appl.ClientID == 4 &&
                                    (app.IsDeleted == false ||
                                     app.IsDeleted == null)
                                group new {app, appStatus, refStatus} by new
                                {
                                    app.ApplicationGenID
                                }
                                into g
                                select new
                                {
                                    ApplicationGenID = (int?) g.Key.ApplicationGenID,
                                    ApplicationStatusGenID = (int?) g.Max(p => p.appStatus.ApplicationStatusGenID),
                                    ApplicationStatusDesc = g.Min(p => p.refStatus.ApplicationStatusDesc),
                                    ApplicationStatusDate = (DateTime?) g.Max(p => p.appStatus.StatusDate)
                                }).ToList();

需要LINQ to SQL帮助

2 个答案: