<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default4.aspx.cs" Inherits="Default4" %>
                 
     
        
              
              
          
     

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;public partial class Default4 : System.Web.UI.Page{    DataClasses2DataContext context = new DataClasses2DataContext();//linQ方式获取数据库数据    List
     
       lc = new List
      
       ();//初始化一个Chinastates类的泛型集合    protected void Page_Load(object sender, EventArgs e)    {        DropDownList1.SelectedIndexChanged += DropDownList1_SelectedIndexChanged;//委托方法便捷写法，如果需要查询该方法，把光标移动到要找的对象上，按F12自动跳转        DropDownList2.SelectedIndexChanged += DropDownList2_SelectedIndexChanged;        lc = context.ChinaStates.ToList();//lc接受调取数据库里Chinastates转换为list集合的形式数据        if(IsPostBack==false)//只加载一遍        {            //省数据        List
       
         sheng = lc.Where(r => r.ParentAreaCode == "0001").ToList();//调取省的数据        DropDownList1.DataSource = sheng;//将DropDownList1的数据指向sheng        DropDownList1.DataTextField = "AreaName";//DropDownList1的文本文件的名称为AreaName        DropDownList1.DataValueField = "AreaCode";//DropDownList1的值得文件名称为AreaCode        DropDownList1.DataBind();//DropDownList1绑定数据            //市数据        List
        
          shi = lc.Where(r => r.ParentAreaCode == DropDownList1.SelectedItem.Value).ToList();        DropDownList2.DataSource = shi;        DropDownList2.DataTextField = "AreaName";        DropDownList2.DataValueField = "AreaCode";        DropDownList2.DataBind();            //县数据        List
         
           xian = lc.Where(r => r.ParentAreaCode == DropDownList2.SelectedItem.Value).ToList();        DropDownList3.DataSource = xian;        DropDownList3.DataTextField = "AreaName";        DropDownList3.DataValueField = "AreaCode";        DropDownList3.DataBind();        }    }    void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)    {        //县数据        List
          
            xian = lc.Where(r => r.ParentAreaCode == DropDownList2.SelectedItem.Value).ToList(); DropDownList3.DataSource = xian; DropDownList3.DataTextField = "AreaName"; DropDownList3.DataValueField = "AreaCode"; DropDownList3.DataBind(); } void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { //市数据 List
           
             shi = lc.Where(r => r.ParentAreaCode == DropDownList1.SelectedItem.Value).ToList(); DropDownList2.DataSource = shi; DropDownList2.DataTextField = "AreaName"; DropDownList2.DataValueField = "AreaCode"; DropDownList2.DataBind(); //县数据 List
            
              xian = lc.Where(r => r.ParentAreaCode == DropDownList2.SelectedItem.Value).ToList(); DropDownList3.DataSource = xian; DropDownList3.DataTextField = "AreaName"; DropDownList3.DataValueField = "AreaCode"; DropDownList3.DataBind(); }}