动态生成DropDownList 并取值

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);  
    }  
}

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原文地址：https://www.cnblogs.com/jkyweb/p/4992067.html