Database
Create Table [DBO]. [linkage01] (
[ID] [int] identity (1, 1) not null,
[Name] [varchar] (50) Collate chinese_prc_ci_as null
) On [primary]
Go
Create Table [DBO]. [linkage02] (
[ID] [int] identity (1, 1) not null,
[Lid] [int] not null,
[Name] [varchar] (50) Collate chinese_prc_ci_as not null
) On [primary]
Go
Page index. aspx
<% @ Page Language = "C #" autoeventwireup = "true" codefile = "index. aspx. cs" inherits = "_ Index" %>
<HTML>
<Head runat = "server">
<Title> linkagetest. </title>
<Script language = "JavaScript">
// The JB function initializes XMLHTTP Objects Based on Different browsers.
Function JB ()
{
VaR A = NULL;
Try
{
A = new activexobject ("msxml2.xmlhttp ");
}
Catch (E)
{
Try
{
A = new activexobject ("Microsoft. XMLHTTP ");
}
Catch (oc)
{
A = null
}
}
If (! A & typeof XMLHttpRequest! = "Undefined ")
{
A = new XMLHttpRequest ()
}
Return
}
// The following Go function is called when the parent list box is changed. The parameter is the selected entry.
Function go ()
{
VaR svalue = Document. getelementbyid ("ddl01"). value; // obtain the value from the drop-down list in the selection box.
VaR weburl = "index. aspx? Id = "+ svalue; // defines the page for Data Processing
VaR XMLHTTP = JB (); // initialize XMLHTTP objects
XMLHTTP. Open ("get", weburl, true); // submit data. The first parameter is preferably get, and the third parameter is preferably true.
// Alert (XMLHTTP. responsetext );
// If data is successfully returned
XMLHTTP. onreadystatechange = function ()
{
If (XMLHTTP. readystate = 4) // 4 indicates that data is returned successfully.
{
Var result = xmlhttp. responseText; // get the data returned by the server
Document. getElementById ("ddl02"). length = 0; // clear all ddlC drop-down items first
Document. getElementById ("ddl02 "). options. add (new Option ("select", "0"); // add all models to ddlC. Note that Option is not option
If (result! = "") // If the returned data is not empty
{
Var allArray = result. split (","); // splits the received string into arrays according
// Loop this array, note that it starts from 1, because the first character of the received string is, number, so the first array after segmentation is empty
For (var I = 1; I <allArray. length; I ++)
{
Var thisArray = allArray [I]. split ("|"); // splits the string into an array according to |
// Add entries for ddlC
Document. getElementById ("ddl02"). options. add (new Option (thisArray [0]. toString (), thisArray [1]. toString ()));
}
}
}
}
// Send data. Pay attention to the sequence and parameters. The parameter must be null or ""
Xmlhttp. send (null );
}
</SCRIPT>
</Head>
<Body>
<Form ID = "form1" runat = "server">
<Div>
Province: <select id = "ddl01" name = "ddl01" runat = "server" onchange = "Go (this)"> </SELECT>
City: <select id = "ddl02" name = "ddl02" runat = "server"> </SELECT>
<% --
Save: <asp: dropdownlist id = "ddl01" runat = "server" onchange = "Go (this)"> </ASP: dropdownlist>
City: <asp: dropdownlist id = "ddl02" runat = "server"> </ASP: dropdownlist>
-- %>
<Asp: Button ID = "btnOk" runat = "server" Text = "Confirm" OnClick = "btnOk_Click"/>
</Div>
</Form>
</Body>
</Html>
Class file index. cs
Using System;
Using System. Data;
Using System. Configuration;
Using System. Web;
Using System. Web. Security;
Using System. Web. UI;
Using System. Web. UI. WebControls;
Using System. Web. UI. WebControls. WebParts;
Using System. Web. UI. HtmlControls;
Using System. Data. SqlClient;
Public partial class _ index: System. Web. UI. Page
{
Private sqlconnection con;
Private sqldataadapter SDA;
Private sqlcommand cmd;
Private dataset Ds;
Private sqldatareader SDR;
// Database connection string
Public static string constr = "Server =.; database = test; uid = sa; Pwd = sa ";
Protected void page_load (Object sender, eventargs E)
{
Try
{
If (! Ispostback)
{
Con = new SqlConnection (conStr );
Sda = new SqlDataAdapter ("select * from LinkAge01", con );
Ds = new DataSet ();
Sda. Fill (ds, "LinkAge01 ");
Ds. Tables ["LinkAge01"]. DefaultView. Sort = "id asc ";
Ddl01.DataSource = ds. Tables ["LinkAge01"]. DefaultView;
Ddl01.DataValueField = "id ";
Ddl01.DataTextField = "name ";
Ddl01.DataBind ();
}
Response. Write ("Request. Form [ddl02]:" + Request. Form ["ddl02"] + "<br/> ");
BindDrop ();
}
Catch (Exception ex)
{
Response. Write ("error:" + ex. ToString ());
}
}
Protected void btnOk_Click (object sender, EventArgs e)
{
Try
{
Response. Write (ddl01.Items [ddl01.SelectedIndex]. Text + "<br/> ");
Response. Write (ddl02.Items [ddl02.SelectedIndex]. Text + "<br/> ");
}
Catch (Exception ex)
{
Response. Write ("error:" + ex. ToString ());
}
}
Protected void BindDrop ()
{
String str = Request. QueryString ["id"];
String str1 = ddl01.Items [ddl01.SelectedIndex]. Value;
Response. Write ("str1 =" + str1 + "<br/> ");
String a = str + "abc ";
If (str + "abc "! = "Abc") // If str is added with a string! = The original string indicates that the onchange event of ddlS has been triggered.
Bindchild (STR); // triggers the onchange event of ddls.
Else
Bindparent (str1); // The first time a live refresh is loaded
}
Protected void bindparent (string str1)
{
Try
{
// If this is the first request or the page is refreshed, select the value of ddls.
// Convert the parameter to int
Int I = convert. toint32 (str1 );
Ddl02.items. Clear ();
Ddl02.Items. Add (new ListItem ("select", "0 "));
Con = new SqlConnection (conStr );
Cmd = new SqlCommand ("select * from LinkAge02 where lID =" + I, con );
Con. Open ();
Sdr = cmd. ExecuteReader ();
While (sdr. Read ())
{
Ddl02.Items. Add (new ListItem (sdr ["name"]. ToString (), sdr ["id"]. ToString ()));
}
SDR. Close ();
Con. Close ();
Ddl02.items [0]. Selected = true;
Ddl01.items [0]. Selected = false;
// Add the following statement to save the status of the second ddl02 when you click the submit button to submit the form.
Response. Write ("request. Form [ddl02]:" + request. Form ["ddl02"] + "<br/> ");
Ddl02.value = request. Form ["ddl02"];
}
Catch (Exception ex)
{
Response. Write ("error:" + ex. ToString ());
}
}
Protected void BindChild (String str)
{
// The content added to any controls including dropdownlist through js will not be saved
// Convert the parameter to int
Int I = Convert. ToInt32 (str );
String result = "";
Response. Clear ();
Con = new SqlConnection (conStr );
Cmd = new SqlCommand ("select * from LinkAge02 where lID =" + I, con );
Con. Open ();
Sdr = cmd. ExecuteReader ();
While (sdr. Read ())
{
Result + = "," + sdr ["name"]. ToString () + "|" + sdr ["id"]. ToString ();
}
Sdr. Close ();
Con. Close ();
Response. Write (result );
Response. Flush ();
Response. Close ();
}
}
Address: http://blog.csdn.net/mathew3625/archive/2008/04/13/2288707.aspx
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