LINQ to SQL查询使用“NOT IN”

Question

可以使用 LINQ to SQL 查询 NOT IN 吗？

例如，SELECT au_lname, state FROM authors WHERE state NOT IN ('CA', 'IN', 'MD')

- jinsungy

Answer 1

    List<string> states = new List<string> { "CA", "IN", "MD" };
    var q = from a in authors
            where !states.Contains(a.state)
            select new { a.au_lname, a.state };

或者

   var q = authors.Where( a => !states.Contains( a.state ) )
                  .Select( a => new { a.au_lname, a.state } );

- Buzzer

Answer 2

您可以使用Contains实现此操作：

       var states = new[]  {"CA", "IN", "MD"};
       var query = db.Authors.Where(x => !states.Contains(x.state));

- CMS

Answer 3

这里有一个例子：

NorthwindDataContext dc = new NorthwindDataContext();
dc.Log = Console.Out;
var query =
    from c in dc.Customers
    where !(from o in dc.Orders
            select o.CustomerID)
           .Contains(c.CustomerID)
    select c;
foreach (var c in query) Console.WriteLine( c );

- Galwegian

---

主查询内使用Contains/!Contains即可，没有必要进行子查询。 - Rob

Answer 4

是的！

这里有一个我们已经编写好的代码示例：

            List<long> badUserIDs = new List { 10039309, 38300590, 500170561 };
            BTDataContext dc = new BTDataContext();
            var items = from u in dc.Users
                        where !badUserIDs.Contains(u.FbUserID)
                        select u;

生成的SQL如下：

{SELECT [t0].[UserID], [t0].[FbUserID], [t0].[FbNetworkID], [t0].[Name], FROM [dbo].[Users] AS [t0] WHERE NOT ([t0].[FbUserID] IN (@p0, @p1, @p2)) }

- Rob