省市选择器[数据绑定]

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aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="省市级联数据绑定.aspx.cs" Inherits="简单绑定.省市级联数据绑定" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using 数据导入导出练习;
using System.Data.SqlClient;

namespace 简单绑定
{
    public partial class 省市级联数据绑定 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                SqlDataReader reader = sqlhelper.datareader("select * from p");
                if (reader.HasRows)
                {
                    DropDownList1.DataSource = reader;//读取表中的省份
                    DropDownList1.DataTextField = "p";//将表中的省份名称绑定到控件的字段名上
                    DropDownList1.DataValueField = "id";//将表中的id绑定到控件的value上
                    DropDownList1.DataBind();//进行数据绑定
                    DropDownList1.SelectedIndex = 0;//默认选择项为第一项
                    //以下是初始化城市列表用的
                    string value = DropDownList1.SelectedValue;
                    SqlDataReader reader2 = sqlhelper.datareader("select * from city where pid=@pid", new SqlParameter("@pid", value));
                    if (reader2.HasRows)
                    {
                        DropDownList2.DataSource = reader2;
                        DropDownList2.DataTextField = "city";
                        DropDownList2.DataValueField = "id";
                        DropDownList2.DataBind();
                    }
                }
            }
        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            string value=DropDownList1.SelectedValue;
            SqlDataReader reader = sqlhelper.datareader("select * from city where pid=@pid", new SqlParameter("@pid", value));
            if (reader.HasRows)
            {
                DropDownList2.DataSource = reader;
                DropDownList2.DataTextField = "city";
                DropDownList2.DataValueField = "id";
                DropDownList2.DataBind();
            }
        }
    }
}