Ajax简单示例之改变下拉框动态生成表格

1.建立一个aspx页面，html代码 < html  xmlns ="http://www.w3.org/1999/xhtml"   > < head  runat ="server" >      < title > Untitled Page </ title >      < script  type ="text/javascript" >         var xmlHttp;        function createXMLHttpRequest()         {            if (window.ActiveXObject)             {                xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");            }             else if (window.XMLHttpRequest)             {                xmlHttp = new XMLHttpRequest();            }        }                    function startRequest()         {            //debugger;            var ProvinceID=document.getElementById("DropDownList1");                       createXMLHttpRequest();            xmlHttp.onreadystatechange = handleStateChange;            xmlHttp.open("GET", "?ProvinceID="+ProvinceID.value, true);            xmlHttp.send(null);        }                    function handleStateChange()         {            if(xmlHttp.readyState == 4) //0(未初始化);1(正在装载);2 (装载完毕);3 (交互中);4 (完成)             {                if(xmlHttp.status == 200) //200(OK);404(not found)                {                    document.getElementById("gridiv").innerHTML=xmlHttp.responseText;                }            }        }         </ script > </ head > < body >      < form  id ="form1"  runat ="server" >      < div >          < asp:DropDownList  ID ="DropDownList1"  runat ="server" >          </ asp:DropDownList >         </ div >      < div  id  ="gridiv" ></ div >      </ form > </ body > </ html > 2.cs代码 using  System.Data.SqlClient; protected   void  Page_Load( object  sender, EventArgs e)     {        if (!Page.IsPostBack)        {            this.DropDownList1.Attributes.Add("onchange", "return startRequest();");            ListProvince();            if (ProvinceID != "")            {                GetCityByProvinceID(ProvinceID);            }        }    }      property #region property    private string ProvinceID    {        get        {            if (Request["ProvinceID"] != null && Request["ProvinceID"].ToString() != "")            {                return Request["ProvinceID"];            }            else            {                return "";            }        }    }    #endregion      GetDataSet #region GetDataSet    private DataSet GetDataSet(string sql)    {        string constring=System.Configuration.ConfigurationSettings.AppSettings["ConnectionString"];        SqlDataAdapter    sda =new SqlDataAdapter(sql,constring);        DataSet ds=new DataSet();        sda.Fill(ds);        return ds;    }    #endregion      GetCityByProvinceID #region GetCityByProvinceID    private void GetCityByProvinceID(string ProvinceID)    {        string connStr = ConfigurationSettings.AppSettings["ConnectionString"];        SqlConnection conn = new SqlConnection(connStr);        string sql = "select * from city where father='" + ProvinceID + "'";        SqlCommand cmd = new SqlCommand(sql, conn);        conn.Open();        SqlDataReader dr = cmd.ExecuteReader();        string s = @"<table cellspacing='0' cellpadding='4' border='0' id='GridView1' style='color:#333333;border-collapse:collapse;'>";        s+="<tr style='color:White;background-color:#990000;font-weight:bold;'>";            s+="<th scope='col'>流水号</th><th scope='col'>代号</th><th scope='col'>城市</th></tr>";        int m = 0;        while (dr.Read())        {            if (m % 2 == 0)            {                s += "<tr style='color:#333333;background-color:#FFFBD6;'>";            }            else            {                s += "<tr style='color:#333333;background-color:White;'>";            }            m++;            s += "<td>" + dr["id"] + "</td>";            s += "<td>" + dr["cityID"] + "</td>";            s += "<td>" + dr["city"] + "</td>";            s += "</tr>";        }                s+="</table>";        dr.Close();        conn.Close();        this.Response.Write(s);        this.Response.End();    }    #endregion      ListProvince #region ListProvince    private void ListProvince()    {        string sql = "select * from province";        DataSet ds = GetDataSet(sql);        DropDownList1.DataSource = ds;        DropDownList1.DataTextField = "province";        DropDownList1.DataValueField = "provinceID";        DropDownList1.DataBind();    }    #endregion 3.示例数据库下载 area1.rar