相关疑难解决方法(0)

我列出了人员的姓名和名字,以及人员姓名和姓氏的清单.有些人没有名字,有些人没有姓氏; 我想在两个列表上进行完全外连接.

所以以下列表:

ID  FirstName
--  ---------
 1  John
 2  Sue

ID  LastName
--  --------
 1  Doe
 3  Smith

应该产生:

ID  FirstName  LastName
--  ---------  --------
 1  John       Doe
 2  Sue
 3             Smith

我是LINQ的新手(如果我是跛脚的话,请原谅我)并找到了很多"LINQ Outer Joins"的解决方案,这些解决方案看起来非常相似,但实际上似乎是留下了外部联接.

到目前为止,我的尝试是这样的:

private void OuterJoinTest()
{
    List<FirstName> firstNames = new List<FirstName>();
    firstNames.Add(new FirstName { ID = 1, Name = "John" });
    firstNames.Add(new FirstName { ID = 2, Name = "Sue" });

    List<LastName> lastNames = new List<LastName>();
    lastNames.Add(new LastName { ID = 1, Name = "Doe" …

我正在尝试LINQ实体.

我有以下问题:我希望它这样做:

SELECT 
     T_Benutzer.BE_User
    ,T_Benutzer_Benutzergruppen.BEBG_BE
FROM T_Benutzer

LEFT JOIN T_Benutzer_Benutzergruppen
    ON T_Benutzer_Benutzergruppen.BEBG_BE = T_Benutzer.BE_ID 

我最接近的是这个:

        var lol = (
            from u in Repo.T_Benutzer

            //where u.BE_ID == 1
            from o in Repo.T_Benutzer_Benutzergruppen.DefaultIfEmpty()
                // on u.BE_ID equals o.BEBG_BE

            where (u.BE_ID == o.BEBG_BE || o.BEBG_BE == null)

            //join bg in Repo.T_Benutzergruppen.DefaultIfEmpty()
            //    on o.BEBG_BG equals bg.ID

            //where bg.ID == 899 

            orderby
                u.BE_Name ascending
                //, bg.Name descending

            //select u 
            select new
            {
                 u.BE_User
                ,o.BEBG_BG
                //, bg.Name 
            }
         ).ToList();

但是这会产生与内部联接相同的结果,而不是左联接.
而且,它创建了这个完全疯狂的SQL:

SELECT 
     [Extent1].[BE_ID] AS [BE_ID] …

SELECT
  e.EmpName,
  me.RemarkNumber,
  me.RemarkPeopleNumber
FROM
  EmployeeInfo e
  LEFT JOIN (
    SELECT
      COUNT(RemarkId) As RemarkNumber,
      COUNT(DISTINCT MemberId) As RemarkPeopleNumber,
      CreateUser
    FROM
      MemberRemark
    WHERE
      RemarkStatus = 0
    GROUP BY
      CreateUser
  ) AS me On e.EmpName = me.CreateUser
WHERE
  BranchCode = '0000'
  And [Status] = 0

如何将其转换为 LINQ？

from e in db.EmployeeInfo
join me in (
    from memberRemarks in db.MemberRemark
    where memberRemarks.RemarkStatus == 0
    group memberRemarks by new
    {
        memberRemarks.CreateUser,
    } into g
    select new
    {
        RemarkNumber = g.Count(),
        RemarkPeopleNumber = g.Select(m => …

我有一个用于替换数据库函数的 Linq 查询。这是第一个有多个连接的，我似乎无法弄清楚为什么它返回 0 结果。

如果您能看到任何可能导致错误返回的差异，将不胜感激......我一直在尝试解决它的时间比我应该有的时间更长。

Linq 查询

context.StorageAreaRacks
    .Join(context.StorageAreas, sar => sar.StorageAreaId, sa => sa.Id, (sar, sa) => new { sar, sa })
    .Join(context.StorageAreaTypes, xsar => xsar.sar.StorageAreaId, sat => sat.Id, (xsar, sat) => new { xsar, sat })
    .Join(context.Racks, xxsar => xxsar.xsar.sar.RackId, r => r.Id, (xxsar, r) => new { xxsar, r })
    .Where(x => x.xxsar.sat.IsManual == false)
    .Where(x => x.r.IsEnabled == true)
    .Where(x => x.r.IsVirtual == false)
    .Select(x => new { x.xxsar.sat.Id, x.xxsar.sat.Name })
    .Distinct()
    .ToList();

这是由 LINQ …

我想在 EF Core 中创建一个查询，如下所示：

SELECT SUM(DATEDIFF(DAY, FromDate, ToDate)) AS Diff 
FROM Table1

上述查询适用于 T-SQL - 如何在 Linq 中创建查询？