Question

const empty = []
const typeofNumber = (x) => ( typeof x === 'number' )

console.log(`an empty array will return ${empty.every(typeofNumber)} on an every, since "every" predicate fulfilled the condition`)

if(empty.length && empty.every(typeofNumber)) {
  console.log('empty array length and every are truthy')
} else {
  console.log('empty array length and every are falsey')
}

if(empty && empty.every(typeofNumber)) {
  console.log('empty array and every are truthy')
} else {
  console.log('empty array and every are falsey')
}

我试图弄清楚如何使用LINQ将其转换为C＃。我是C＃和LINQ的新手，无法正确启动我的子查询。你们其中一个巫师可以为我开灯吗？

更新-----------------

我想我已经得到了它的主旨，但是在查询最大启动日期时遇到了麻烦：

SELECT ra.ResidentID, ra.RoomID, r.Number, ra.StartDate, p.FacilityID
FROM( 
    SELECT ResidentID, MAX(StartDate) AS max_start
    FROM RoomAssignments
    GROUP BY ResidentID
    ) m

    INNER JOIN RoomAssignments ra
        ON ra.ResidentID = m.ResidentID
        AND ra.StartDate = m.max_start

    INNER JOIN Rooms r
        ON r.ID = ra.RoomID

    INNER JOIN Person p 
        ON p.ID = ra.ResidentID

    inner join ComplianceStage cs 
        ON cs.Id = p.ComplianceStageID

ORDER BY ra.EndDate DESC

Answer 1

在我的LINQ to SQL Recipe之后，如果你只是遵循SQL，那么转换非常简单。唯一棘手的部分是join范围变量，从最大开始日期的子查询到RoomAssignments中与字段名称匹配的新匿名对象。

var maxQuery = from mra in RoomAssignments
               group mra by mra.ResidentID into mrag
               select new { ResidentID = mrag.Key, MaxStart = mrag.Max(mra => mra.StartDate) };

var ans = from m in maxQuery
          join ra in RoomAssignments on m equals new { ra.ResidentID, MaxStart = ra.StartDate }
          join r in Rooms on ra.RoomID equals r.ID
          join p in Persons on ra.ResidentID equals p.ID
          join cs in ComplianceStage on p.ComplianceStageID equals cs.Id
          orderby ra.EndDate descending
          select new {
            ra.ResidentID,
            ra.RoomID,
            r.Number,
            ra.StartDate,
            p.FacilityID
          };

需要帮助将SQL转换为LINQ

1 个答案: