SelectedItems 属性是非通用的 IList 。您不能简单地将其转换为通用的 IList< T> 。

The type of the SelectedItems property is the non-generic IList. You can't simply cast that to the generic IList<T>.

然而，您可以使用 LINQ 获取 IEnumerable< x> 或列表< x> 。

You could however use LINQ to get an IEnumerable<x> or a List<x>.

using System.Linq;

IList list = obj as IList;
IEnumerable<x> SelectedItemsList = list.Cast<x>();
// or 
List<x> SelectedItemsList = list.Cast<x>().ToList();