1     class parent
 2     {
 3         public string name { get; set; }
 4     }
 5     class sub : parent { }
 6 
 7              #region 由派生類集合強轉成父類集合（正確）
 8             List<sub> sublist = new List<sub> { new sub { name = "zzl" }, new sub { name = "zhz" } };
 9             sublist.Cast<parent>().ToList().ForEach(i => Console.WriteLine(i.name));
10             #endregion
11 
12             #region 由父類集合強轉成派生類集合(出錯)
13             List<parent> parentlist = new List<parent> { new sub { name = "zzl" }, new parent { name = "zhz" } };
14             parentlist.Cast<sub>().ToList().ForEach(i => Console.WriteLine(i.name));
15             #endregion