Question

我知道有很多类似的问题，我已经解决了很多问题，但是仍然无法掌握如何在LINQ中解决问题。我需要创建一个查询来获取数据，作为此纯SQL查询：

SELECT p.ProcessId, p.Description, p.StartedOn, p.StartedBy, uuus.Name + ' ' + uuus.Surname AS StartedByName, p.FinishedOn, p.FinishedBy, uuu.Name + ' ' + uuu.Surname as FinishedByName, p.PlannedFinish, p.PlannedStart, COUNT(CASE WHEN h.IsCompleted IS NULL AND h.HandlingId IS NOT NULL THEN 1 END)
FROM JDE_Processes p LEFT JOIN JDE_Users uuu ON p.FinishedBy = uuu.UserId LEFT JOIN JDE_Handlings h ON h.ProcessId=p.ProcessId LEFT JOIN JDE_Users uuus ON uuus.UserId=p.StartedBy
GROUP BY p.ProcessId, p.Description, p.StartedOn, p.StartedBy,uuus.Name + ' ' + uuus.Surname, p.FinishedOn, p.FinishedBy, uuu.Name + ' ' + uuu.Surname, p.PlannedFinish, p.PlannedStart, p.Createdon
ORDER BY p.CreatedOn DESC

这是我的linq版本，大多数情况下都可以运行，但是我无法弄清楚“如果h.IsCompleted = 0计数”部分。

var items = (from p in db.JDE_Processes
    join uuu in db.JDE_Users on p.FinishedBy equals uuu.UserId into finished
    from fin in finished.DefaultIfEmpty()
    join h in db.JDE_Handlings on p.ProcessId equals h.ProcessId into hans
    from ha in hans.DefaultIfEmpty()
    group new { p, fin }
    by new {
        p.ProcessId,
        p.Description,
        p.StartedOn,
        p.StartedBy,
        p.FinishedOn,
        p.FinishedBy,
        p.PlannedFinish,
        p.PlannedStart,
        fin.Name,
        fin.Surname
    } into grp
    orderby grp.Key.ProcessId descending
    select new Process
    {
        ProcessId = grp.Key.ProcessId,
        Description = grp.Key.Description,
        StartedOn = grp.Key.StartedOn,
        StartedBy = grp.Key.StartedBy,
        FinishedOn = grp.Key.FinishedOn,
        FinishedBy = grp.Key.FinishedBy,
        FinishedByName = grp.Key.Name + " " + grp.Key.Surname,
        PlannedStart = grp.Key.PlannedStart,
        PlannedFinish = grp.Key.PlannedFinish,
        HandlingStatus = grp.Count().ToString()
    });

问题：

1）如何获取“如果h.IsCompleted = 0起作用”的计数？

2）我可以使用某种别名吗？我的意思是，在此查询的实际版本中，还有另一个左联接join uuu in db.JDE_Users on p.StartedBy equals uuu.UserId into started from star in started.DefaultIfEmpty() 这导致我在grp中有2个Name和2个Surname列。然后如何将适当的字段分配给适当的输出字段？我的意思是这样：

select new Process
{
    ProcessId = grp.Key.ProcessId,
    Description = grp.Key.Description,
    StartedOn = grp.Key.StartedOn,
    StartedBy = grp.Key.StartedBy,
    StartedByName = grp.Key.Name + " " + grp.Key.Surname, // <-- how will it know which Name field to use? 
    FinishedOn = grp.Key.FinishedOn,
    FinishedBy = grp.Key.FinishedBy,
    FinishedByName = grp.Key.Name + " " + grp.Key.Surname,
    PlannedStart = grp.Key.PlannedStart,
    PlannedFinish = grp.Key.PlannedFinish,
    HandlingStatus = grp.Count().ToString()
}

Answer 1

我不确定这将有多大帮助，因为它是您的SQL的翻译，并且您的LINQ似乎与您的SQL没有关系，但是我有：

var ans = from p in db.JDE_Processes
          join uuu in db.JDE_Users on p.FinishedBy equals uuu.UserId into uuuj
          from uuu in uuuj.DefaultIfEmpty()
          join h in db.JDE_Handlings on p.ProcessId equals h.ProcessId into hj
          from h in hj
          group new { p, h } by new { p.ProcessId, p.Description, p.StartedOn, p.StartedBy, p.FinishedOn, p.FinishedBy, p.PlannedFinish, p.PlannedStart } into phg
          select new {
              phg.Key.ProcessId,
              phg.Key.Description,
              phg.Key.StartedOn,
              phg.Key.StartedBy,
              phg.Key.FinishedOn,
              phg.Key.FinishedBy,
              phg.Key.PlannedFinish,
              phg.Key.PlannedStart,
              HandlingStatus = phg.Where(ph => ph.h.IsCompleted == null).Count()
          };

Answer 2

很抱歉回答我自己的问题，但我已经找到2的答案。当我有两个同名的属性（例如“姓”）时，我只是不知道如何为属性创建别名。请在下面找到包含别名以及NetMage解决的条件计数器部分的代码：

Response

在Linq's Group中按左连接的多列进行条件计数

2 个答案: