<HTML>
<Head>
<Title> Ajax implementation without any new three linkage drop-down box </title>
<Meta content = "Microsoft Visual Studio. NET 7.1" name = "generator">
<Meta content = "C #" name = "code_language">
<Meta content = "JavaScript" name = "vs_defaultclientscript">
<Meta content = "http://schemas.microsoft.com/intellisense/ie5" name = "vs_targetschema">
<Script language = "JavaScript">
// City ------------------------------
Function cityresult ()
{
VaR city = Document. getelementbyid ("dropdownlist1 ");
Ajaxmethod. getcitylist (city. Value, get_city_result_callback );
}
Function get_city_result_callback (response)
{
If (response. value! = NULL)
{
// Debugger;
Document. All ("dropdownlist2"). Length = 0;
VaR DS = response. value;
If (Ds! = NULL & typeof (DS) = "object" & Ds. tables! = NULL)
{
For (VAR I = 0; I <Ds. Tables [0]. Rows. length; I ++)
{
VaR name = Ds. Tables [0]. Rows [I]. City;
VaR id = Ds. Tables [0]. Rows [I]. cityid;
Document. All ("dropdownlist2"). Options. Add (New Option (name, ID ));
}
}
}
Return
}
// City ----------------------------------------
Function arearesult ()
{
VaR area = Document. getelementbyid ("dropdownlist2 ");
Ajaxmethod. getarealist (area. Value, get_area_result_callback );
}
Function get_area_result_callback (response)
{
If (response. value! = NULL)
{
Document. All ("dropdownlist3"). Length = 0;
VaR DS = response. value;
If (Ds! = NULL & typeof (DS) = "object" & Ds. tables! = NULL)
{
For (VAR I = 0; I <Ds. Tables [0]. Rows. length; I ++)
{
VaR name = Ds. Tables [0]. Rows [I]. area;
VaR id = Ds. Tables [0]. Rows [I]. areaid;
Document. All ("dropdownlist3"). Options. Add (New Option (name, ID ));
}
}
}
Return
}
Function getdata ()
{
VaR province = Document. getelementbyid ("dropdownlist1 ");
VaR pindex = province. selectedindex;
VaR pvalue = province. Options [pindex]. value;
VaR ptext = province. Options [pindex]. text;
VaR city = Document. getelementbyid ("dropdownlist2 ");
VaR cIndex = city. selectedindex;
VaR cvalue = city. Options [cIndex]. value;
VaR ctext = city. Options [cIndex]. text;
VaR area = Document. getelementbyid ("dropdownlist3 ");
VaR aindex = area. selectedindex;
VaR avalue = area. Options [aindex]. value;
VaR atext = area. Options [aindex]. text;
VaR TXT = Document. getelementbyid ("textbox1 ");
Document. getelementbyid ("<% = textbox1.clientid %> "). innertext = "province:" + pvalue + "|" + ptext + "City:" + cvalue + "|" + ctext + "area: "+ avalue +" | "+ atext;
}
</SCRIPT>
</Head>
<Body ms_positioning = "gridlayout">
<Form ID = "form1" method = "Post" runat = "server">
<Table id = "Table1" style = "Z-INDEX: 101; left: 96px; position: absolute; top: 32px" cellspacing = "1"
Cellpadding = "1" width = "300" border = "1" bgcolor = "# ccff66">
<Tr>
<TD> province and city </TD>
<TD> <asp: dropdownlist id = "dropdownlist1" runat = "server"> </ASP: dropdownlist> </TD>
</Tr>
<Tr>
<TD> city </TD>
<TD> <asp: dropdownlist id = "dropdownlist2" runat = "server"> </ASP: dropdownlist> </TD>
</Tr>
<Tr>
<TD> city </TD>
<TD> <asp: dropdownlist id = "dropdownlist3" runat = "server"> </ASP: dropdownlist> </TD>
</Tr>
</Table>
<Asp: textbox id = "textbox1" style = "Z-INDEX: 102; left: 416px; position: absolute; top: 48px" runat = "server"
Width = "pixel PX"> </ASP: textbox> <input style = "Z-INDEX: 103; left: 456px; width: 56px; position: absolute; top: 96px; height: 24px"
Type = "button" value = "test" onclick = "getdata ();">
</Form>
</Body>
</Html> 2.cs Code
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;
Namespace ajaxtest
{
/** // <Summary>
/// Summary description for webform1.
/// </Summary>
Public class webform1: system. Web. UI. Page
{
Protected system. Web. UI. webcontrols. dropdownlist dropdownlist1;
Protected system. Web. UI. webcontrols. dropdownlist dropdownlist2;
Protected system. Web. UI. webcontrols. textbox textbox1;
Protected system. Web. UI. webcontrols. dropdownlist dropdownlist3;
Private void page_load (Object sender, system. eventargs E)
{
Ajax. Utility. registertypeforajax (typeof (ajaxmethod ));
If (! Page. ispostback)
{
This. dropdownlist1.datasource = ajaxmethod. getprovincelist ();
This. dropdownlist1.datatextfield = "Province ";
This. dropdownlist1.datavaluefield = "provinceid ";
This. dropdownlist1.databind ();
This. dropdownlist1.attributes. Add ("onclick", "cityresult ();");
This. dropdownlist2.attributes. Add ("onclick", "arearesult ();");
}
}
Web Form Designer generated code # region web form designer generated code
Override protected void oninit (eventargs E)
{
//
// Codegen: This call is required by the ASP. NET web form designer.
//
Initializecomponent ();
Base. oninit (E );
}
/** // <Summary>
/// Required method for designer support-do not modify
/// The contents of this method with the code editor.
/// </Summary>
Private void initializecomponent ()
{
This. Load + = new system. eventhandler (this. page_load );
}
# Endregion
}
} 3. ajaxmethod
Using system;
Using system. Data;
Using system. Data. sqlclient;
Namespace ajaxtest
{
/** // <Summary>
/// Summary description for ajaxmethod.
/// </Summary>
Public class ajaxmethod
{
Getprovincelist # region getprovincelist
Public static dataset getprovincelist ()
{
String SQL = "select * From Province ";
Return getdataset (SQL );
}
# Endregion
Getcitylist # region getcitylist
[Ajax. ajaxmethod (Ajax. httpsessionstaterequirement. Read)]
Public dataset getcitylist (INT provinceid)
{
String SQL = "select * from city where Father =" + provinceid;
Return getdataset (SQL );
}
# Endregion
Getarealist # region getarealist
[Ajax. ajaxmethod (Ajax. httpsessionstaterequirement. Read)]
Public dataset getarealist (INT cityid)
{
String SQL = "select * from area where Father =" + cityid;
Return getdataset (SQL );
}
# Endregion
getdataset # region getdataset
Public static dataset getdataset (string SQL)
{< br> string connectionstring = system. configuration. configurationsettings. appsettings ["connectionstring"];
sqldataadapter SDA = new sqldataadapter (SQL, connectionstring);
dataset DS = new dataset ();
SDA. fill (DS);
return Ds;
}< BR ># endregion
}< BR >} 4. web. config
5. ajax. DLL download/files/singw.ine/ajax.rar