C# 中为什么List<List<T>> 不能转换为 IList<IList<T>> ? 第1页

       public interface IList<T> : ICollection<T>, IEnumerable<T>, IEnumerable      

       using System.Collections.Generic; using System.Linq;  class Record {   public List<Record> Data {     get { return null; }   } }  class Program {   static void Main(string[] args) {     var records = new List<Record>();     var casted1 = (IList<IList<Record>>)records.Select(r => r.Data as IList<Record>).ToList(); // ok     Console.WriteLine("cast1 succeeded.");     var casted2 = (IList<IList<Record>>)records.Select(r => r.Data).ToList<IList<Record>>(); // ok     Console.WriteLine("cast2 succeeded.");     var casted3 = (IList<IList<Record>>)records.Select(r => r.Data).ToList(); // fail     Console.WriteLine("cast3 succeeded.");   } }