C# c Linq连接同一个表两次

使用下面的linq语句，我显示了一个结果列表，我将其连接到两个名为AssetTransferItems和Memberships的表中。Memberships表包含一个用户列表，其中每个用户都存储为GUID并包含其用户名

现在我想添加另一个名为UserReceived的列，并像UserAdded一样显示用户名而不是GUID。UserReceived=txboxItems.UserReceived当前显示GUID，我正在尝试获取用户名

我不确定如何修改Linq语句以从UserReceived的成员资格表中获取用户名。我添加了第二个连接：

join userReceived in Memberships on txboxItems.UserReceived equals userReceived.UserId

但这并没有显示结果

    var query = (from txboxItems in AssetTransferItems
                                        join user in Memberships on txboxItems.UserAdded equals user.UserId
                                        join userReceived in Memberships on txboxItems.UserReceived equals userReceived.UserId

                                     where txboxItems.TransferBoxID == BoxId && txboxItems.Deleted == false
                                    orderby txboxItems.TicketID descending
                                     select new
                                    {
                                        Description = txboxItems.Description.ToString(),
                                        DateAdded = (DateTime?) txboxItems.DateAdded.Value,
                                        UserAdded = user.Username,
                                        DateReceived = (DateTime?) txboxItems.DateReceived.Value,
                                        UserReceived = userReceived.Username,
                                    });

编辑：我更新了linq语句以反映我现在拥有的内容。它显示userReceived.Username，但不显示userReceived为null的所有其他结果

多谢各位

join user in Memberships on txboxItems.UserAdded equals user.UserId
join userReceived in Memberships on txboxItems.UserAdded equals userReceived.UserId

应该是：

join user in Memberships on txboxItems.UserAdded equals user.UserId
join userReceived in Memberships on txboxItems.UserReceived equals userReceived.UserId
// ------------------------------------------------^^^^^^^^

然后您应该能够使用

UserReceived = userReceived.Username

而不是

UserReceived = txboxItems.UserReceived
// ------------^^^^^^^^^^^^^^^^^^^^^^^

编辑

从中，为了示例的可读性，我删除了where和orderby子句：

from txboxItems in AssetTransferItems
from user in Memberships
    .Where(u => u.UserId == txboxItems.UserAdded).DefaultIfEmpty()
from userReceived in Memberships
    .Where(u => u.UserId == txboxItems.UserReceived).DefaultIfEmpty()
select new
{
     Description = txboxItems.Description.ToString(),
     DateAdded = (DateTime?) txboxItems.DateAdded.Value,
     UserAdded = user?.Username,
     DateReceived = (DateTime?) txboxItems.DateReceived.Value,
     UserReceived = userReceived?.Username
}

---

如果您只想使用“userReceived.Username”执行某些操作，为什么还要第三次加入？为什么不能像使用user.Username一样使用“userReceived.Username”呢？有一个输入错误，很抱歉，添加了一个连接太多次，但被删除了..那么使用userReceived.Username有什么不好的地方呢？就像你使用的user.Username一样？我尝试了userReceived.Username，但结果只有在userReceived不为null时才会显示。我之前尝试过这个，但是，它从未返回任何结果，只返回具有不为null的ReceivedUser的结果。@Belliez我编辑了我的答案，添加了您似乎需要的左连接行为。这很完美，谢谢。我还有一些类似的陈述，我可以重复使用你的例子，再次感谢