掌握TreeView用法

DAL层代码：
 1 using System.Collections.Generic;
 2 using System.Data;
 3 using DataTreeModel;
 4 using System.Data.SqlClient;
 5 using System.Windows.Forms;
 6
 7 namespace DataTreeDAL
 8 {
 9     class TreesNodeDAL
10     {
11         //根据Parentid返回表中所有的的实体对象
12         public IEnumerable<ItemsNode> GetEveryOneByParent(int id)
13         {
14         DataTable dt=sqlHelper.GetDatatable("select * from ItemsNode where parentId =@id",
15             new SqlParameter("id",id));
16         List<ItemsNode> list = new List<ItemsNode>();
17             foreach (DataRow row in dt.Rows)
18             {
19                 list.Add(CreateItemsNose(row));//添加对象
20             }
21             return list;
22         }
23         //更新表中的记录
24         public int UpdateRecord(ItemsNode item)
25         {
26          return sqlHelper.ExecuteNonQuery("update ItemsNode set name=@name,content=@content where id=@id", new SqlParameter("name", item.name), new SqlParameter("content", item.content),new
27              SqlParameter("id",item.Id));
28         }
29
30         public int InsertRecord(ItemsNode item)
31         {
32             return sqlHelper.ExecuteNonQuery("Insert into ItemsNode (name,content,parentId) values(@name,@content,@parentId)", new SqlParameter("name", item.name), new SqlParameter("content", item.content), new
33             SqlParameter("parentId", item.parentId));
34         }