C# 將List轉成樹的兩種方式(遞歸、循環)

背景

將一個具有ChildCode(子節點)和ParentCode(父節點)的list集合轉換成樹狀結構。

生成數據基本格式，如下圖：

 最終展示樣式，如下圖：

（注:如果你對樣式沒要求，可以使用layui的樹形組件，簡單方便-https://www.layui.com/demo/tree.html）

　　有兩種轉換方式，一種是普通的遞歸，一種是雙層循環。數據量非很大的情況下，遞歸的效率相比雙層循環來說，效率高一些。
　　注：不要循環調用數據庫，最好將數據根據條件全部查詢出來，然后進行處理。

准備工作

聲明一個Model類：

public class TreeNode { /// <summary>
    /// 子id /// </summary>
    public string Id { get; set; } /// <summary>
    /// 父id /// </summary>
    public string ParentId { get; set; } /// <summary>
    /// 名稱 /// </summary>
    public string Name { get; set; } /// <summary>
    /// 子節點 /// </summary>
    public List<TreeNode> Children { get; set; } /// <summary>
    /// 無參構造函數 /// </summary>
    public TreeNode() { Children = new List<TreeNode>(); } /// <summary>
    /// 有參構造函數 /// </summary>
    /// <param name="id">子id</param>
    /// <param name="name">名稱</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>
    /// 有參構造函數 /// </summary>
    /// <param name="id">子id</param>
    /// <param name="name">名稱</param>
    /// <param name="parent">父節點</param>
    public TreeNode(string id, string name, TreeNode parent) { this.Id = id; this.Name = name; this.ParentId = parent.Id; Children = new List<TreeNode>(); } }

生成一個轉換前的list集合：

TreeNode treeNode1 = new TreeNode("1", "山東", "0"); TreeNode treeNode2 = new TreeNode("2", "北京", "0"); TreeNode treeNode3 = new TreeNode("3", "歷下區", treeNode1); TreeNode treeNode4 = new TreeNode("4", "高新區", treeNode1); TreeNode treeNode5 = new TreeNode("5", "歷城區", treeNode1); TreeNode treeNode6 = new TreeNode("6", "甸柳庄", treeNode3); TreeNode treeNode7 = new TreeNode("7", "濟南長途汽車站東站", treeNode6); TreeNode treeNode8 = new TreeNode("8", "朝陽區", treeNode2); TreeNode treeNode9 = new TreeNode("9", "海淀區", treeNode2); TreeNode treeNode10 = new TreeNode("10", "金盞鄉", 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);

遞歸方式

調用方式：

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

實現代碼：

/// <summary>
/// 使用遞歸方法建樹 /// </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; }

 

雙層循環

調用方式：

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

實現代碼：

/// <summary>
/// 雙層循環 /// </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; } }  

代碼下載 

百度雲盤：鏈接：https://pan.baidu.com/s/1XLP7kl3RuadT2y12VmOHeQ 提取碼：6mlj

 

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