public void LoopToAppendChildren(List<NewsType> all,  NewsType curItem)
    var subItems = all.Where(ee => ee.ParentId==curItem.Id).ToList(); 
    curItem.children = new List<NewsType>();
    curItem.children.AddRange(subItems);
    foreach (var subItem in subItems)
        LoopToAppendChildren(all, subItem);//新闻1.1
//通用 ParentId,Id,children 用了反射效率不高
 public void LoopToAppendChildren<T>(List<T> all, T curItem, string parentIdName = "ParentId", string idName = "Id", string childrenName = "children")
        {
  var subItems = all.Where(ee => ee.GetType().GetProperty(parentIdName).GetValue(ee, null).ToString() == curItem.GetType().GetProperty(idName).GetValue(curItem, null).ToString()).ToList(); //新闻1
  curItem.GetType().GetProperty(childrenName).SetValue(curItem, subItems);
  foreach (var subItem in subItems)
  {
    LoopToAppendChildren(all, subItem);//新闻1.1
  }
 }
//实例化一个根节点
NewsType rootRoot = new NewsType();
rootRoot.Id = 0;
rootRoot.ParentId = 0;  
rootRoot.Name="根节点";
LoopToAppendChildren(dc.NewsType.ToList(), rootRoot);