C# TreeHelper帮助类

/// <summary>
    /// 树结构帮助类
    /// </summary>
    public class TreeHelper
    {
        #region 外部接口

        /// <summary>
        /// 建造树结构
        /// </summary>
        /// <param name="allNodes">所有的节点</param>
        /// <returns></returns>
        public static List<T> BuildTree<T>(List<T> allNodes) where T : TreeModel, new()
        {
            List<T> resData = new List<T>();
            var rootNodes = allNodes.Where(x => x.ParentId == "0" || x.ParentId.IsNullOrEmpty()).ToList();
            resData = rootNodes;
            resData.ForEach(aRootNode =>
            {
                if (HaveChildren(allNodes, aRootNode.Id))
                    aRootNode.Children = GetChildren(allNodes, aRootNode);
            });

            return resData;
        }

        /// <summary>
        /// 获取所有子节点
        /// 注：包括自己
        /// </summary>
        /// <typeparam name="T">节点类型</typeparam>
        /// <param name="allNodes">所有节点</param>
        /// <param name="parentNode">父节点</param>
        /// <param name="includeSelf">是否包括自己</param>
        /// <returns></returns>
        public static List<T> GetChildren<T>(List<T> allNodes, T parentNode, bool includeSelf) where T : TreeModel
        {
            List<T> resList = new List<T>();
            if (includeSelf)
                resList.Add(parentNode);
            _getChildren(allNodes, parentNode, resList);

            return resList;

            void _getChildren(List<T> _allNodes, T _parentNode, List<T> _resNodes)
            {
                var children = _allNodes.Where(x => x.ParentId == _parentNode.Id).ToList();
                _resNodes.AddRange(children);
                children.ForEach(aChild =>
                {
                    _getChildren(_allNodes, aChild, _resNodes);
                });
            }
        }

        #endregion

        #region 私有成员

        /// <summary>
        /// 获取所有子节点
        /// </summary>
        /// <typeparam name="T">树模型（TreeModel或继承它的模型）</typeparam>
        /// <param name="nodes">所有节点列表</param>
        /// <param name="parentNode">父节点Id</param>
        /// <returns></returns>
        private static List<object> GetChildren<T>(List<T> nodes, T parentNode) where T : TreeModel, new()
        {
            Type type = typeof(T);
            var properties = type.GetProperties().ToList();
            List<object> resData = new List<object>();
            var children = nodes.Where(x => x.ParentId == parentNode.Id).ToList();
            children.ForEach(aChildren =>
            {
                T newNode = new T();
                resData.Add(newNode);

                //赋值属性
                properties.Where(x => x.CanWrite).ForEach(aProperty =>
                {
                    var value = aProperty.GetValue(aChildren, null);
                    aProperty.SetValue(newNode, value);
                });
                //设置深度
                newNode.Level = parentNode.Level + 1;

                if (HaveChildren(nodes, aChildren.Id))
                    newNode.Children = GetChildren(nodes, newNode);
            });

            return resData;
        }

        /// <summary>
        /// 判断当前节点是否有子节点
        /// </summary>
        /// <typeparam name="T">树模型</typeparam>
        /// <param name="nodes">所有节点</param>
        /// <param name="nodeId">当前节点Id</param>
        /// <returns></returns>
        private static bool HaveChildren<T>(List<T> nodes, string nodeId) where T : TreeModel, new()
        {
            return nodes.Exists(x => x.ParentId == nodeId);
        }
        #endregion
    }

　　扩展方法：

    public static partial class Extention
    {
        /// <summary>
        /// 判断是否为Null或者空
        /// </summary>
        /// <param name="obj">对象</param>
        /// <returns></returns>
        public static bool IsNullOrEmpty(this object obj)
        {
            if (obj == null)
                return true;
            else
            {
                string objStr = obj.ToString();
                return string.IsNullOrEmpty(objStr);
            }
        }

        /// <summary>
        /// 给IEnumerable拓展ForEach方法
        /// </summary>
        /// <typeparam name="T">模型类</typeparam>
        /// <param name="iEnumberable">数据源</param>
        /// <param name="func">方法</param>
        public static void ForEach<T>(this IEnumerable<T> iEnumberable, Action<T> func)
        {
            foreach (var item in iEnumberable)
            {
                func(item);
            }
        }
    }