C# 将List转成树的两种方式(递归、循环)

背景

将一个具有ChildCode(子节点)和ParentCode(父节点)的list集合转换成树状结构。

生成数据基本格式，如下图：

 最终展示样式，如下图：

（注:如果你对样式没要求，可以使用layui的树形组件，简单方便-https://www.layui.com/demo/tree.html）

　　有两种转换方式，一种是普通的递归，一种是双层循环。数据量非很大的情况下，递归的效率相比双层循环来说，效率高一些。
　　注：不要循环调用数据库，最好将数据根据条件全部查询出来，然后进行处理。

准备工作

声明一个Model类：

public class TreeNode { /// <summary>
    /// 子id /// </summary>
    public string Id { get; set; } /// <summary>
    /// 父id /// </summary>
    public string ParentId { get; set; } /// <summary>
    /// 名称 /// </summary>
    public string Name { get; set; } /// <summary>
    /// 子节点 /// </summary>
    public List<TreeNode> Children { get; set; } /// <summary>
    /// 无参构造函数 /// </summary>
    public TreeNode() { Children = new List<TreeNode>(); } /// <summary>
    /// 有参构造函数 /// </summary>
    /// <param name="id">子id</param>
    /// <param name="name">名称</param>
    /// <param name="parentId">父id</param>
    public TreeNode(string id, string name, string parentId) { this.Id = id; this.Name = name; this.ParentId = parentId; Children = new List<TreeNode>(); } /// <summary>
    /// 有参构造函数 /// </summary>
    /// <param name="id">子id</param>
    /// <param name="name">名称</param>
    /// <param name="parent">父节点</param>
    public TreeNode(string id, string name, TreeNode parent) { this.Id = id; this.Name = name; this.ParentId = parent.Id; Children = new List<TreeNode>(); } }

生成一个转换前的list集合：

TreeNode treeNode1 = new TreeNode("1", "山东", "0"); TreeNode treeNode2 = new TreeNode("2", "北京", "0"); TreeNode treeNode3 = new TreeNode("3", "历下区", treeNode1); TreeNode treeNode4 = new TreeNode("4", "高新区", treeNode1); TreeNode treeNode5 = new TreeNode("5", "历城区", treeNode1); TreeNode treeNode6 = new TreeNode("6", "甸柳庄", treeNode3); TreeNode treeNode7 = new TreeNode("7", "济南长途汽车站东站", treeNode6); TreeNode treeNode8 = new TreeNode("8", "朝阳区", treeNode2); TreeNode treeNode9 = new TreeNode("9", "海淀区", treeNode2); TreeNode treeNode10 = new TreeNode("10", "金盏乡", treeNode8); List<TreeNode> list = new List<TreeNode>(); list.Add(treeNode1); list.Add(treeNode2); list.Add(treeNode3); list.Add(treeNode4); list.Add(treeNode5); list.Add(treeNode6); list.Add(treeNode7); list.Add(treeNode8); list.Add(treeNode9); list.Add(treeNode10);

递归方式

调用方式：

List<TreeNode> trees1 = TreeHelper.BulidTreeByRecursive(list, new List<TreeNode>(), "0");

实现代码：

/// <summary>
/// 使用递归方法建树 /// </summary>
public static List<TreeNode> BulidTreeByRecursive(List<TreeNode> treeNodes, List<TreeNode> resps, string pID) { resps = new List<TreeNode>(); List<TreeNode> tempList = treeNodes.Where(c => c.ParentId == pID).ToList(); for (int i = 0; i < tempList.Count; i++) { TreeNode node = new TreeNode(); node.Id = tempList[i].Id; node.ParentId = tempList[i].ParentId; node.Name = tempList[i].Name; node.Children = BulidTreeByRecursive(treeNodes, resps, node.Id); resps.Add(node); } return resps; }

 

双层循环

调用方式：

List<TreeNode> trees = TreeHelper.BulidTree(list);

实现代码：

/// <summary>
/// 双层循环 /// </summary>
/// <param name="treeNodes"></param>
/// <returns></returns>
public static List<TreeNode> BulidTree(List<TreeNode> treeNodes) { try { List<TreeNode> trees = new List<TreeNode>(); foreach (var treeNode in treeNodes) { if ("0" == (treeNode.ParentId)) { trees.Add(treeNode); } foreach (var it in treeNodes) { if (it.ParentId == treeNode.Id) { treeNode.Children.Add(it); } } } return trees; }  catch (Exception ex) { throw ex; } }  

代码下载 

百度云盘：链接：https://pan.baidu.com/s/1XLP7kl3RuadT2y12VmOHeQ 提取码：6mlj

 

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