在網站注冊的頁面上經常要選擇注冊地點，如果改變省的名稱就能出現對應的市級的名稱，將為用戶帶來很大的方便，下面就將我的實現過程給大家看一下

首先，建立數據庫“Place”，表里面的內容如下圖所示：

窗體布局如下圖所示：

下面是實現代碼：

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;

namespace 省市聯動
{
    public partial class 省市聯動 : System.Web.UI.Page
    {
        string strCon = "server=.;database=Place;uid=sa;pwd=123456";
        protected void Page_Load(object sender, EventArgs e)
        {
            //DropDownList1.Text = "北京市";
            if (!IsPostBack)
            {
               
                SqlConnection sqlcon = new SqlConnection(strCon);
                string sqlstr = "select * from Province";
                string strCity = "select * from City where Province = '北京市'";
                SqlDataAdapter myda = new SqlDataAdapter(sqlstr, strCon);
                SqlDataAdapter mydaCity = new SqlDataAdapter(strCity, sqlcon);
                DataSet myds = new DataSet();
                DataSet mydsCity = new DataSet();
                sqlcon.Open();
                myda.Fill(myds);
                mydaCity.Fill(mydsCity);
                DropDownList1.DataSource = myds;
                DropDownList1.DataValueField = "ProvinceName";
                DropDownList1.DataBind();
                DropDownList2.DataSource = mydsCity;
                DropDownList2.DataValueField = "CityName";
                DropDownList2.DataBind();
                sqlcon.Close();
            }
        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            SqlConnection sqlcon = new SqlConnection(strCon);
            string sqlstr = "select * from City where Province = '" + DropDownList1.SelectedValue.Trim() + "'";
            SqlDataAdapter myda = new SqlDataAdapter(sqlstr, sqlcon);
            DataSet myds = new DataSet();
            sqlcon.Open();
            myda.Fill(myds);
            DropDownList2.DataSource = myds;
            DropDownList2.DataValueField = "CityName";
            DropDownList2.DataBind();
            sqlcon.Close();
        }
    }
}
  

DropDownList控件實現省市聯動