Question

departments = (from p in _context.DateSnippets
                               where query.UserInfo.Departments.Contains(p.DepartmentId)
                               group p by p.DepartmentId
                                   into g
                                   select new Tuple<int, DateTime>(g.Key, g.Max(x => x.FromDate))
                               ).ToList();

我为

获得以下例外

包含（）方法

这是例外

An exception of type 'System.NotSupportedException' occurred in mscorlib.dll 
but was not handled in user code
Additional information: Only parameterless constructors and 
initializers are supported in LINQ to Entities.

Answer 1

问题在于：

new Tuple<int, DateTime>(g.Key, g.Max(x => x.FromDate)

不幸的是，当您对数据库执行此操作时，它将无法工作，因为您无法在构造函数中传递参数。许多变通办法之一可能是使用对象

new MyData {Key = g.Key, Date = g.Max(x => x.FromDate)}

Answer 2

将Contains更改为Any

where query.UserInfo.Departments.Any(d => d.DepartmentId == p.DepartmentId)

将选择更改为投射到烦人的课程或poco。该错误明确声明您不能在构造函数

中包含参数

 select new 
 {
  g.Key,
  g.Max(x => x.FromDate)
 }

EntityFramework包含不起作用

2 个答案: