c# - Linq 中的 Sql IN 子句等效

Question

我想在 linq 的 cluase 中使用 sql，因为我尝试过包含但它显示错误。我的代码是..

 var allId = new int[] { 31, 32, 33 };
 var libraryList = from c in db.COURSELIBRARies
                   join cc in db.COURSECATEGORYTAGGINGs on c.LIBITEMID equals cc.COURSEID
                   where allId.Contains(cc.CATEGORYID) // here error is showing.
                   select new Library { Id = c.LIBITEMID, Name = c.GROUPNAME, Desc = c.DESCRIPTION, logo = c.LOGO, CategoryId = cc.CATEGORYID };

错误是:

'int[]' does not contain a definition for 'Contains' and the best extension method overload 'System.Linq.Queryable.Contains<TSource>(System.Linq.IQueryable<TSource>, TSource)' has some invalid arguments

Instance argument: cannot convert from 'int[]' to 'System.Linq.IQueryable<int?>'

Answer 1

你包括了吗？

using System.Linq;

?

另一个可能的原因是您传递给 Contains() 的值不是 INT。尝试转换:where allId.Contains((int)cc.CATEGORYID)