我正在尝试排除db.AdminAdjusterStatus中存在的具有a.id的项。
from u in db.Users
join a in db.Adjusters on u.id equals a.userID
where u.userType.ToLower() == "adjuster"
&& !(from x in db.AdminAdjusterStatus select x.adjusterID).Contains(a.id)
select new AdjusterProfileStatusItem { user = u, adjuster = a }
上面的代码说，"其中NOT包含db.AdminAdjusterStatus.adjusterID中的a.id。
问题是，它不起作用。我在db.AdminAdjusterStatus:中有这两个条目
A9EC05B5-651D-4AA7-8275-1F6BFE212C031第55d9版0a-4854-9D5F-B89DB17F02D2
而且，LINQ查询给了我：
A9EC05B5-651D-4AA7-8275-1F6BFE212C031第55d9版0a-4854-9D5F-B89DB17F02D2e21f49c-9505-495d-b4a3-259ee3459d6
然而，它应该只给我：
e21f49c-9505-495d-b4a3-259ee3459d6
var query = from u in db.Users
from a in db.Adjusters
where u.userType.ToLower() == "adjuster" &&
u.id == a.userID &&
!db.AdminAdjusterStatus.Any(i => i.adjusterID == a.id)
您可以尝试执行左联接并过滤空记录。如果没有数据进行测试，我无法确定它是否会"开箱即用"，但我已经多次使用以下代码进行这样的过滤：
db.Users.Join(db.Abjusters, outer => outer.id, inner => inner.userID, new { User = outer, Adjuster = inner })
.GroupJoin(DBConcurrencyException.AdminAdjusterStatus, outer => outer.Adjuster.id, inner => inner.adjusterID, new { User = outer.User, Adjuster = outer.Adjuster, Admins = inner })
.SelectMany(grp => grp.Admins.DefaultIfEmpty(), (grp, admin) => new { User = grp.User, Adjuster = grp.Adjuster, Admin = admin })
.Where(item => item.User.userType == "adjuster" && item.Admin == null)
.Select(item => new AdjusterProfileStatusItem { user = item.User, adjuster = item.Adjuster });
GroupJoin/SelectMany组合执行左联接，然后您可以过滤对象为空的地方，这应该会产生与NOT IN相同的结果。
感谢大家的帮助，很抱歉浪费了大家的时间。我意识到这条线：
obj.adjusterID = '@(Url.RequestContext.RouteData.Values["id"])';
在我的代码的其他地方，发送的是u.id，而不是我认为的a.id。因此，我在数据库中保存了错误的ID，从而导致了我遇到的问题。
再次感谢您的帮助！
也许这可行？
var AdjusterItems = from aa in AdminAdjusterStatus
join a in Adjusters
on aa.AdjusterId equals a.AdjusterId
select a.UserId;
var UsersNotAdjustAdmin = from u in Users
where !AdjusterItems.Any(x => x == u.Id)
&& u.UserType.Equals("Adjuster", StringComparison.InvariantCultureIgnoreCase)
select u;
var result = from u in UsersNotAdjustAdmin
join a in Adjusters
on u.Id equals a.UserId
select new AdjusterProfileStatusItem() { Adjuster = a, User = u };