跪求linq语句，大神在哪里？
已知一个树形泛型集合和一个实体类

public class  Group
{
    /// <summary>
    /// 编号
    /// </summary>
    public string ID {get;set;}
    /// <summary>
    /// 父级编号
    /// </summary>
    public string ParentID{get;set;}
    /// <summary>
    /// 等级
    /// </summary>
    public int Levels{get;set;}
    /// <summary>
    /// 次数
    /// </summary>
    public int Num{get;set;}
    /// <summary>
    /// 排名 
    /// </summary>
    public int No{get;set;}
}

  List<Group> list = new List<Group>();
  list.Add(new Group { Id = "01", ParentID = "-1", Levels = "-1",Num=21 });
  list.Add(new Group { Id = "02", ParentID = "01", Levels = "1",Num=5 });
  list.Add(new Group { Id = "04", ParentID = "02", Levels = "2",Num=1 });
  list.Add(new Group { Id = "05", ParentID = "02", Levels = "2",Num=4 });                
  list.Add(new Group { Id = "03", ParentID = "01",  Levels = "1",Num=16 });
  list.Add(new Group { Id = "06", ParentID = "03",  Levels = "2",Num=10 });
  list.Add(new Group { Id = "07", ParentID = "03",  Levels = "2",Num=3 });
  list.Add(new Group { Id = "08", ParentID = "03",  Levels = "2",Num=3 });

问题：根据等级和次数排名，同等级同次数排名相同
{linq 语句}

结果：保持树形结果不变
No ID ParentID Levels Num
1 01 -1 -1 21
1 03 01 1 16
1 06 03 2 10
3 07 03 2 3
3 08 03 2 3
2 02 01 1 5
2 05 02 2 4
4 04 02 2 1


[解决办法]
你这结果哪里是按等级先排序啊，分吗是乱的
Levels 应该是整形
List<Group> arr = list.OrderBy(x => x.Levels).ThenBy(y => y.Num).ToList();
[解决办法]
排序如1楼
我设计的话ParentID后就不会有Levels
[解决办法]
那你直接用TreeView或者TreeListView。查出某个节点下的数据，排序后再按顺序加载上去，用不着一次全部排序。
[解决办法]
这样的设计太蛋疼，这样的排序更蛋疼

或许这个可以帮到你: http://blog.csdn.net/q107770540/article/details/7708418