Using Ajax in ASP.net to realize the DropDownList of continuous motion

Ajax|asp.net

The following code can be used absolutely, or you can implement multilevel menus ....

<script language= "JavaScript" >
function Load (state)
{
var drp2 = document.getElementById ("DropDownList2");
for (Var i=0;i<=drp2.options.length-1;i++)
{
Drp2.remove (i);
}
var ohttpreq = new ActiveXObject ("MSXML2.    XMLHTTP "); Send Request
var odoc = new ActiveXObject ("MSXML2.    DOMDocument "); Response results
var State=document.getelementbyid ("DropDownList1"). Value;
Ohttpreq.open ("Post", "Webform2.aspx?state=" +state, false);
Ohttpreq.send ("");
result = Ohttpreq.responsetext;
Odoc.loadxml (result);

Items = Odoc.selectnodes ("//city/table");
Items = Odoc.selectnodes ("//address/table");
for (var item = Items.nextnode (); item;item = Items.nextnode ())
{
var city = Item.selectsinglenode ("//address"). nodeTypedValue;
var newoption = document.createelement ("option");
Newoption.text = City;
Newoption.value = City;
Drp2.options.add (newoption);
}
}
</script>

============================

WebForm1.aspx

private void Page_Load (object sender, System.EventArgs e)
  {
  // Place user code here to initialize page
   if (! IsPostBack)
   {
    sqlconnection con = new SqlConnection ("Packet Size=4096;user Id=sa ;d ata source=server;persist Security info=false;initial catalog=pubs ");
    SqlDataAdapter da = new SqlDataAdapter ("Select state from authors group by state", con);
    DataSet ds = new DataSet ("state");
    da. Fill (DS);
    this. Dropdownlist1.datasource = ds. Tables[0];
    this. Dropdownlist1.datatextfield = "state";
    this.　Dropdownlist1.datavaluefield = "state";
    this.　　Dropdownlist1.databind ();
    this.　　DROPDOWNLIST1.ATTRIBUTES.ADD ("onchange", "Load ()");
   //dropdownlist1.
  }
 
 }

Webform2.aspx

private void Page_Load (object sender, System.EventArgs e)
{
Place user code here to initialize page
if (this. request["State"]!=null)
{
String state = this. request["State"]. ToString ();
SqlConnection con = new SqlConnection ("Packet size=4096;user id=sa;data source=server;persist security info=false; Initial catalog=pubs ");
SqlDataAdapter da = new SqlDataAdapter ("Select address from authors where State = '" +state+ "", con);
DataSet ds = new DataSet ("Address");
Da. Fill (DS);
XmlTextWriter writer = new XmlTextWriter (Response.outputstream, response.contentencoding);
Writer. formatting = formatting.indented;
Writer. indentation = 4;
Writer. IndentChar = ';
Ds. WriteXml (writer);
Writer. Flush ();
Response.End ();
Writer. Close ();
}
}