c# - 多对多表上的 LEFT LINQ TO SQL C# JOIN

Question

您好，我是 linq to sql 的新手，我了解基础知识。问题是我想在查询中进行左连接。查询中有 3 个表。

1. Claimants ( all rows should be returned from this table)
2. Claim
3. User

查询应该返回所有拥有 claim 人的用户。这是通过多对多表声明完成的。但是，无论用户如何，都应退还所有 claim 人。因此，左边加入了 Claimants。

我有以下查询

    var d = (from Claimants in DB.Claimants
                 join Claims in DB.Claims on Claimants.Claiment_ID equals Claims.Claiment_ID
                 join Users in DB.Users on Claims.User_ID equals Users.User_ID
                 where (Claimants.TrialDate.Value >= dtDayStart & Claimants.TrialDate <= dtDayEnd)
                 select new
                 {
                     ClaimantFirstName = Claimants.FirstName,
                     ClaimantLasname = Claimants.LastName,
                     ClaimantsID = Claimants.IDNumber,
                     Claimants.OurReference,
                     Claimants.TrialDate,
                     InterviewStart = Claims.DateTimeStart,
                     InterviewEnd = Claims.DateTimeEnd,
                     Claims.Priority,
                     UserFirstname = Users.FirstName,
                     UserLastName = Users.LastName,
                     UserID = Users.IDNumber
                 });

我试过如下使用 into 语句，但没有成功

        var d = (from Claimants in DB.Claimants
                 join Claims in DB.Claims on Claimants.Claiment_ID equals Claims.Claiment_ID
                 into TheClaimants
                 from Claims in TheClaimants.DefaultIfEmpty()

                 join Users in DB.Users on Claims.User_ID equals Users.User_ID
                 where (Claimants.TrialDate.Value >= dtDayStart & Claimants.TrialDate <= dtDayEnd)
                 select new
                 {
                     ClaimantFirstName = Claimants.FirstName,
                     ClaimantLasname = Claimants.LastName,
                     ClaimantsID = Claimants.IDNumber,
                     Claimants.OurReference,
                     Claimants.TrialDate,
                     InterviewStart = Claims.DateTimeStart,
                     InterviewEnd = Claims.DateTimeEnd,
                     Claims.Priority,
                     UserFirstname = Users.FirstName,
                     UserLastName = Users.LastName,
                     UserID = Users.IDNumber
                 });

如果有人能为我指出正确的方向，让我知道如何正确地使用这些左右联接并解释其工作原理，我将不胜感激。非常感谢您。

Answer 1

var d = (from Claimants in DB.Claimants
  join Claims in DB.Claims on Claimants.Claiment_ID equals Claims.Claiment_ID)
  .DefaultIfEmpty()
  join Users in DB.Users on Claims.User_ID equals Users.User_ID
  where (Claimants.TrialDate.Value >= dtDayStart & Claimants.TrialDate <= dtDayEnd)
  .DefaultIfEmpty()
  select new
  {
    ClaimantFirstName = Claimants.FirstName,
    ClaimantLasname = Claimants.LastName,
    ClaimantsID = Claimants.IDNumber,
    Claimants.OurReference,
    Claimants.TrialDate,
    InterviewStart = Claims.DateTimeStart,
    InterviewEnd = Claims.DateTimeEnd,
    Claims.Priority,
    UserFirstname = Users.FirstName,
    UserLastName = Users.LastName,
    UserID = Users.IDNumber
 });

Left outter join