C#构建树形数据结构

转自：https://www.jb51.net/article/125747.htm

树形结构：最近在做任务管理，任务可以无限派生子任务且没有数量限制，前端采用Easyui的Treegrid树形展示控件。

a.JSON数据格式：

[
  {
    "children":[
      {
        "children":[

        ],
        "username":"username2",
        "password":"password2",
        "id":"2",
        "pId":"1",
        "name":"节点2"
      },
      {
        "children":[

        ],
        "username":"username2",
        "password":"password2",
        "id":"A2",
        "pId":"1",
        "name":"节点2"
      }
    ],
    "username":"username1",
    "password":"password1",
    "id":"1",
    "pId":"0",
    "name":"节点1"
  }

]

　　

b.定义实体必要字段

为了Tree结构的通用性，我们可以定义一个抽象的公用实体TreeObject以保证后续涉及到的List<T>转化树形JSON

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MyTree.Abs
{
  public class TreeObejct
  {
    public string id { set; get; }
    public string pId { set; get; }
    public string name { set; get; }
    public IList<TreeObejct> children = new List<TreeObejct>();
    public virtual void Addchildren(TreeObejct node)
    {
      this.children.Add(node);
    }
  }
}

　　c.实际所需实体TreeModel让它继承TreeObject,这样对于id,pId,name,children我们就可以适用于其它实体了，这也相当于我们代码的特殊约定：

using MyTree.Abs;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MyTree.Models
{
  public class TreeModel : TreeObejct
  {
    public string username { set; get; }
    public string password { set; get; }
  }
}

　　

2、递归遍历

获取全部任务并转化为树形

获取全部任务转化为树形是比较简单的，我们首先获取到pId=0的顶级数据(即不存在父级的任务),我们通过顶级任务依次递归遍历它们的子节点。

 /      //递归获取所有树结构的数据
        public  IList<TreeObject> GetData()
        {
            List<TreeObject> nodes = _context.Node.Where(x => x.parent_node_id == 0).Select(x=>new TreeObject { id=x.id,pId=x.parent_node_id,name=x.name}).ToList();
            foreach(TreeObject item in nodes)
            {
                item.children = GetChildrens(item);
            }
            return nodes;
        }
        //递归获取子节点
        public IList<TreeObject> GetChildrens(TreeObject node)
        {
            IList<TreeObject> childrens = _context.Node.Where(c => c.parent_node_id == node.id).Select(x => new TreeObject { id = x.id, pId = x.parent_node_id, name = x.name }).ToList();
            foreach (TreeObject item in childrens)
            {
                item.children = GetChildrens(item);
            }
            return childrens;
        }

3、非递归遍历

非递归遍历在操作中不需要递归方法的参与即可实现Tree的拼接

对于以上的代码，我们不需要修改，只需要定义一个非递归遍历方法NotRecursion：

public static void NotRecursion()
{
  #region 非递归遍历

  System.Diagnostics.Stopwatch sw2 = new System.Diagnostics.Stopwatch();

  sw2.Start();
  Dictionary<string, TreeObejct> dtoMap = new Dictionary<string, TreeObejct>();
  foreach (var item in models)
  {
    dtoMap.Add(item.id, item);
  }
  IList<TreeObejct> result = new List<TreeObejct>();
  foreach (var item in dtoMap.Values)
  {
    if (item.pId == "0")
    {
      result.Add(item);
    }
    else
    {
      if (dtoMap.ContainsKey(item.pId))
      {
        dtoMap[item.pId].AddChilrden(item);
      }
    }

  }

  sw2.Stop();
  Console.WriteLine("----------非递归遍历用时：" + sw2.ElapsedMilliseconds + "----------线程名称：" + t2.Name + ",线程ID：" + t2.ManagedThreadId);

  #endregion

　　main.cs

private static IList<TreeObejct> models;
private static IList<TreeObejct> models2;
private static Thread t1;
private static Thread t2;
static void Main(string[] args)
{
  int count = 6;
  Console.WriteLine("生成任务数："+count+"个");
  models = GetData(count);
  models2 = GetData(count);
  t1 = new Thread(Recursion);
  t2 = new Thread(NotRecursion);
  t1.Name = "递归遍历";
  t2.Name = "非递归遍历";
  t1.Start();
  t2.Start();

  Console.Read();
}