A no refresh two-level linkage drop-down list, the same applies to Firefox, this is Ajax Mody?

ajax| Refresh | no Refresh | dropdown | drop down list

Perhaps "excellent" will bring a lot of criticism, but I think it's really good, and I've seen about 20 flash-free drop-down lists, and they're a mess underneath Firefox. I've been doing this for two days, and that's how if you submit a form, you can keep the value of the second list box, because you pass the JS Add an entry to the Drop-down box so his state is not saved, do not know this is Ajax?
Test platform: Ie6,firefox
Function: Two-level non-flush connection
Features: cross-browser, submit the form to take the value of the second Drop-down box, data from the database, XMLHTTP to send the request, the implementation of no refresh
Request: If you can find a better way please tell me, thank you very much, your criticism and suggestion is a great encouragement to me.
WebForm1.aspx:
<%@ Page language= "C #" codebehind= "WebForm1.aspx.cs" autoeventwireup= "false" inherits= "drop. WebForm1 "%>



WebForm1

runat= "Server" >
Motorola
Nokia

runat= "Server" >
text= "button" >




Backstage WebForm1.aspx.cs:
Using System;
Using System.Collections;
Using System.ComponentModel;
Using System.Data;
Using System.Drawing;
Using System.Web;
Using System.Web.SessionState;
Using System.Web.UI;
Using System.Web.UI.WebControls;
Using System.Web.UI.HtmlControls;
Using System.Configuration;
Using System.Data.SqlClient;

A summary description of the

namespace drop
{
 ///

 ///WebForm1.
 ///
 public class WebForm1:System.Web.UI.Page
 {
   protected System.Web.UI.WebControls.DropDownList dlistparent;
  protected System.Web.UI.WebControls.Button Button1;
  protected System.Web.UI.WebControls.DropDownList Dlistchild;
 
  private void Page_Load (object sender, System.EventArgs e)
  {
    //Place the user code here to initialize the page
   //if (! IsPostBack)
   //{
    binddrop ();//This cannot be placed in the IF (! IsPostBack) inside the
   //}
  

protected void Binddrop ()
{
First I want the parent DropDownList to bind the database too.
if (! IsPostBack)
//{
Bind parent Dlistparent
Bindparent ();
//}
Get the parent_id value passed over, and if it's the first time he's asked for null
String str = request.querystring["parent_id"];
string str1 = Dlistparent.selectedvalue;;
Response.Write (STR1);
If Str adds a string!= the original string indicates the onchange event that triggered the Dlistparent
if ((str+ "abc")!= "abc")
{
Binding Dlistchild Controls
Bindchild (str);//The value of the Father DropDownList is the argument
}
Else
Bindparent (STR1);
}

protected void Bindparent (String str)
{
If this is the first request or refresh of this page, it is based on the value of Dlistparent.
Converts a parameter to an int
int i = Convert.ToInt32 (str);
DListChild.Items.Clear ();
DLISTCHILD.ITEMS.ADD (New ListItem ("All Models", "0"));
Get the database connection string
String connstr = configurationsettings.appsettings["ConnString"]. ToString ();
Initializing a Conn Object
SqlConnection conn = new SqlConnection (CONNSTR);
Database statements
String commstr = String. Format ("Select Type_value,type_text from Phone_type where parent_id={0}", i);
To establish a database command object
SqlCommand comm = new SqlCommand (commstr,conn);
Open Database
Conn. Open ();
Execute command
SqlDataReader dr = Comm. ExecuteReader ();
Loop Dr, add entries to Dlistparent
while (Dr. Read ())
{
DLISTCHILD.ITEMS.ADD (New ListItem (dr[1). ToString (), dr[0]. ToString ()));
I can do that.
DLISTPARENT.ITEMS.ADD (New ListItem (dr["Phone_text"). ToString (), dr["Phone_value"]. ToString ()));
}
Adding the following means that the state of the second dlistchild can be saved when the Point submit button submits the form
Dlistchild.selectedvalue = request.form["Dlistchild"];
Dr. Close ();
Conn. Close ();
}

protected void Bindchild (String str)
{
Content added to any control including DropDownList through JS will not be saved state
Converts a parameter to an int
int i = Convert.ToInt32 (str);
Define a string to save data returned from the database
string result = "";
Empty the output first.
Response.Clear ();
String connstr = configurationsettings.appsettings["ConnString"]. ToString ();
SqlConnection conn = new SqlConnection (CONNSTR);
SqlCommand COMM = conn. CreateCommand ();
String commstr = String. Format ("Select Type_value,type_text from phone_type where parent_id = {0}", i);
Comm.commandtext = Commstr;
Conn. Open ();
SqlDataReader dr = Comm. ExecuteReader ();
while (Dr. Read ())
{
result = "," +dr[0]. ToString () + "|" + dr[1]. ToString ();
DLISTCHILD.ITEMS.ADD (New ListItem (dr[1). ToString (), dr[0]. ToString ()));
}
Output information from the database to the client
Response.Write (Result);
The output finishes closing the response so as not to cause unnecessary output
Response.Flush ();
Response.close ();
Dr. Close ();
Conn. Close ();
}
Code generated #region the Web forms Designer
Override protected void OnInit (EventArgs e)
{
//
CodeGen: This call is required for the ASP.net Web forms Designer.
//
InitializeComponent ();
Base. OnInit (e);
}

Designer supports required methods-do not use the Code editor to modify
The contents of this method.

private void InitializeComponent ()
{
This. Button1.Click + = new System.EventHandler (this. Button1_Click);
This. Load + = new System.EventHandler (this. Page_Load);

}
#endregion

private void Button1_Click (object sender, System.EventArgs e)
{
Response.Write (request.form["Dlistchild"). ToString ());
}
}
}

Data table:
Primary key ID parent_id (int) type_value (int) type_text (varchar)
int increments the value of the parent Drop-down box value drop-down box text