c# 生成树方法

 /// <summary>
    /// 实体类必须实现接口
    /// </summary>
    public interface IToTreeModel
    {
        int Id { get; set; }        
        int ParentId { get; set; }
        List<IToTreeModel> Children { get; set; }
        void AddChilrden(IToTreeModel node);
    }

/// <summary>
    /// 实体类实例
    /// </summary>
    public class ViewModel : IToTreeModel
    {
        public int Id { get; set; }
        public int ParentId { get; set; }
        public string Label { set; get; }    public List<IToTreeModel> Children { get; set; }
        public void AddChilrden(IToTreeModel node)
        {
            if (Children == null)
                Children = new List<IToTreeModel>();
            this.Children.Add(node);
        }
    }

/// <summary>
    /// 处理
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class ToTree<T> where T : IToTreeModel
    {
        public static List<T> ToDo(List<T> models,int ParentId=0,bool IsParentId=true)
        {            
            var dtoMap = new Dictionary<int, T>();
            foreach (var item in models)
            {
                if (!dtoMap.ContainsKey(item.Id))
                {
                    dtoMap.Add(item.Id, item);
                }
            }
            List<T> result = new List<T>();
            foreach (var item in dtoMap.Values)
            {
                if (IsParentId)
                {
                    if (item.ParentId == ParentId)
                    {
                        result.Add(item);
                    }
                    else
                    {
                        if (dtoMap.ContainsKey(item.ParentId))
                        {
                            dtoMap[item.ParentId].AddChilrden(item);
                        }
                    }
                }
                else
                {
                    if (item.Id == ParentId)
                    {
                        result.Add(item);
                    }
                    else
                    {
                        if (dtoMap.ContainsKey(item.ParentId))
                        {
                            dtoMap[item.ParentId].AddChilrden(item);
                        }
                    }
                }                
            }
            return result;
        }
    }

ar list = db.Mode.Select(x => new MenuTree
                {
                    Id = x.ID,
                    Label = x.Name,
                    ParentId = x.ParentId
                }).ToList();
var data = ToTree<MenuTree>.ToDo(list);