动态生成DropDownList

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Default.aspx

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" ><head runat="server">    <title>无标题页</title></head><body>    <form id="form1" runat="server">    <div>          <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>        <br />        <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" /></div>    </form></body></html>

Default.aspx.cs

using System;using System.Data;using System.Configuration;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using Model;using BLL;public partial class _Default : System.Web.UI.Page{    private CategoryBLL _categoryBLL = new CategoryBLL();    private Category _category = new Category();    private void Page_Init(object sender, System.EventArgs e)    {        BindDrpClass();    }    protected void Page_Load(object sender, EventArgs e)    {        string str = "8/14/19/25"; //数据库读取        string[] arr = str.Split('/');        if (arr.Length == PlaceHolder1.Controls.Count) //防止新增类别时读取出错        {            for (int i = 0; i < PlaceHolder1.Controls.Count; i++)            {                if (PlaceHolder1.Controls[i] is DropDownList)                {                    ((DropDownList)PlaceHolder1.Controls[i]).SelectedValue = arr[i];                }            }        }    }      private void BindDrpClass()    {        DataTable dt = _categoryBLL.GetCategory();        DataRow[] drs = dt.Select("pid=0");        foreach (DataRow dr in drs)        {            string id = dr["id"].ToString();            string name = dr["name"].ToString();            DropDownList ddl = new DropDownList();            ddl.Items.Clear();            ddl.ID = "ddl" + id;            ddl.Items.Add(new ListItem("－" + name + "－", id));            PlaceHolder1.Controls.Add(ddl);            int sonparentid = int.Parse(id);            BindDrpNode(sonparentid, dt, ddl);        }    }    private void BindDrpNode(int parentid, DataTable dt, DropDownList ddl)    {        DataRow[] drs = dt.Select("pid= " + parentid);        foreach (DataRow dr in drs)        {            string id = dr["id"].ToString();            string name = dr["name"].ToString();            ddl.Items.Add(new ListItem(name, id));                     PlaceHolder1.Controls.Add(ddl);        }    }    protected void Button1_Click(object sender, EventArgs e)    {        string category = "";        string category2 = "";        foreach (Control childControl in PlaceHolder1.Controls)        {            if (childControl is DropDownList)            {                category += "/" + ((DropDownList)childControl).SelectedItem.Text;                category2 += "/" + ((DropDownList)childControl).SelectedValue;              }        }        if (category.Length > 0)            category = category.Remove(0, 1);        Response.Write(category);        Response.Write("<br />");        if (category2.Length > 0)            category2 = category2.Remove(0, 1);        Response.Write(category2);    }}