省市的二级联动

/**//// <summary>
        /// 省列表框
        /// </summary>
        private void DisplayProvince()
        {
            SqlDataReader sdr=db.RunProcGetReader("select * from Province");
            ddlProvince.DataSource=sdr;
            ddlProvince.DataTextField="ProName";
            ddlProvince.DataValueField="ProID";
            ddlProvince.DataBind();
            sdr.Close();
        }

        /**//// <summary>
        /// 市列表
        /// </summary>
        private void DisplayCity()
        {
            SqlDataAdapter sda=db.CreateDa("select * from City");
            DataTable dt=new DataTable();
            sda.Fill(dt);
            
            //将市数据放入一个label中，此label设置属性隐藏即可
            lblTemp.Text="";
            foreach(DataRow row in dt.Rows)
            {
                lblTemp.Text=lblTemp.Text+row["proid"]+"-"+row["cityid"]+"-"+row["cityname"]+",";
            }
            sda.Dispose();
        }

<script language="javascript">
//将隐藏的字符串取出来，然后分割到一个数组中去
var str = document.getElementById("lblTemp").innerText;
arr=str.split(",");
a=arr.length
ar=new Array()
for (i=0;i<a;i++){
  ar[i]=arr[i].split("-");
}
onecount=ar.length;


//此处实现联动
function  ld() {
  document.Form1.ddlCity.length=0
  lid=Form1.ddlProvince.value;       
  for  (i=0;i<onecount;i++)  { 
    if  (ar[i][0]  ==  lid) {
   document.Form1.ddlCity.options.add(new Option(ar[i][2],  ar[i][1]));    
    }    
  }   
}  
function showMsg()
{
 alert(document.Form1.ddlProvince.value);
 alert(document.Form1.ddlCity.value);
}

        </script>