效果图：
数据库表：
DirID:目录的ID，ParentID：目录的父路径ID，Name：目录的名字
主要代码：
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
public partial class DropdownlistTree : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
DataTable datatable = this.GetDataTable();
DataRow[] row = datatable.Select("ParentID='-1'");
//添加根目录
ListItem li = new ListItem(row[0]["Name"].ToString());
DropDownList1.Items.Add(li);
addOtherDll("", Convert.ToInt32(row[0]["DirID"]), datatable,1);
}
}
/**//// <summary>
/// 添加其他节点
/// </summary>
/// <param name="Pading">空格</param>
/// <param name="DirId">父路径ID</param>
/// <param name="datatable">返回的datatable</param>
/// <param name="deep">树形的深度</param>
private void addOtherDll(string Pading, int DirId, DataTable datatable,int deep)
{
DataRow[] rowlist=datatable.Select("ParentID='"+DirId+"'");
foreach (DataRow row in rowlist)
{
string strPading = "";
for (int j = 0; j < deep; j++)
{
strPading += " "; //用全角的空格
}
//添加节点
ListItem li = new ListItem(strPading + "|--" + row["Name"].ToString());
DropDownList1.Items.Add(li);
//递归调用addOtherDll函数，在函数中把deep加1
addOtherDll(strPading,Convert.ToInt32(row["DirID"]), datatable,deep+1);
}
}
/**//// <summary>
/// 从数据库中读取数据返回datatable
/// </summary>
/// <returns></returns>
private DataTable GetDataTable()
{
SqlConnection conn = newSqlConnection(ConfigurationManager.ConnectionStrings["Personal"].ConnectionString);
SqlDataAdapter adp = new SqlDataAdapter("select * from Test", conn);
DataSet datset = new DataSet();
conn.Open();
adp.Fill(datset, "Test");
return datset.Tables[0];
}
}
当然，当读取DropDownList时若要去除"|--"和空格可以调用addOtherDll.SelectValue().Replace("|--","").Trim()
