DropDownList实现无限分级

数据库：SqlServer2000
表：tree
表结构：

测试数据：

算法：使用递归实现

======================================

asp.net代码：

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

namespace AspNetTest.Common
{
/// <summary>
/// tree 的摘要说明。
/// </summary>

public class tree : System.Web.UI.Page
{

private DataTable dtPowerTree = new DataTable();
  private DataTable dt=new DataTable();
  protected System.Web.UI.WebControls.DropDownList DropDownList1;
  protected System.Web.UI.WebControls.TextBox TextBox1;
  const string tablename = "tree";
  protected System.Web.UI.WebControls.DropDownList DropDownList2;
  private string strText;

  private void Page_Load(object sender, System.EventArgs e)
  {
   if(!Page.IsPostBack)
   {
    FillTreeDataTable();
    blTreeDataTable(0);
    dtPowerTree.Clear();

}

   // 在此处放置用户代码以初始化页面
  }
  private void FillTreeDataTable()
  {
   string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionString"];
   SqlConnection conn = new SqlConnection(ConnectionString);
   SqlDataAdapter da = new SqlDataAdapter("select Id,PowerName,Layer,ParentId from " + tablename, conn);
   da.Fill(dtPowerTree);
  }
  private void blTreeDataTable(int _ParentId)
  {
   string filter = "ParentId=" + _ParentId;
   string sort = "Id ASC";
   DataRow[] drs = dtPowerTree.Select(filter, sort);
   for(int i=0; i<drs.Length; i++)
   {
    if(Convert.ToInt32(drs[i][3]) == _ParentId)
    {
     int Id = Convert.ToInt32(drs[i][0]);
     string PowerName = drs[i][1].ToString();
     int Layer = Convert.ToInt32(drs[i][2]);

for(int n=1;n<=Layer; n++)
     {
      strText += HttpUtility.HtmlDecode("  ");

     }

if(_ParentId!=0)
{

DropDownList1.Items.Add(new ListItem(strText+"┣"+PowerName,Id.ToString()));
      strText="";
     }
     else
     {

DropDownList1.Items.Add(new ListItem(PowerName,Id.ToString()));
}

blTreeDataTable(Id);
    }
   }
  }

#region Web 窗体设计器生成的代码
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
   //
   InitializeComponent();
   base.OnInit(e);
  }

  /// <summary>
  /// 设计器支持所需的方法 - 不要使用代码编辑器修改
  /// 此方法的内容。
  /// </summary>
  private void InitializeComponent()
  {
   this.DropDownList1.SelectedIndexChanged += new System.EventHandler(this.DropDownList1_SelectedIndexChanged);
   this.Load += new System.EventHandler(this.Page_Load);

}
#endregion

}
}

转载于:https://www.cnblogs.com/challenge/archive/2006/07/21/456303.html