Asp.net js three-level linkage menu implementation method (1/3)

Asp tutorial. net js three-level linkage menu implementation method

Available in ie5.5, ie8, firefox 2.0.0.12, chrome 8.0.552.237
In ashx, obtain the corresponding value from the database tutorial through the input parameters.

Parameter name:

Type: The value is regiontwo (indicating that the second-level region is obtained) or regionthree (indicating that the third-level region is obtained ),

Oneid, indicating the first-level region number,

Twoid, indicating the second-level region number

Getregiontwoinfo and getregionthreeinfo are the methods for obtaining the IDs and names of level 2 and Level 3 regions.
Public void processrequest (httpcontext context)
{
String type = context. request. querystring ["type"];
If (type. equals ("regiontwo "))
    {
String oneid = context. request. querystring ["oneid"];
Context. response. contenttype = "text/plain ";
Context. response. write (getregiontwoinfo (oneid ));
    }
Else if (type. equals ("regionthree "))
    {
String oneid = context. request. querystring ["oneid"];
String twoid = context. request. querystring ["twoid"];
Context. response. contenttype = "text/plain ";
Context. response. write (getregionthreeinfo (oneid, twoid ));
    }
}
Js code

Create an xmlhttprequest object, send a request, and set the onreadystatechange function.

Var http_request = false;
Function send_request (url, content, callback)
{
If (window. xmlhttprequest)
  {
Http_request = new xmlhttprequest ();
If (http_request.overridemimetype)
    {
Http_request.overridemimetype ("text/xml ");
    }
  }
Else
  {
Try
    {
Http_request = new activexobject ("msxml2.xmlhttp ");
    }
Catch (e)
    {
Try
      {
Http_request = new activexobject ("microsoft. xmlhttp ");
      }
Catch (e)
      {
      }
    }
  }
   
If (! Http_request)
  {
Window. alert ("You cannot create an xmlhttprequest object instance. ");
Return false;
  }
 
If (navigator. useragent. indexof ("firefox") <0)
Http_request.onreadystatechange = callback;
Http_request.open ("get", url, false );
Http_request.setrequestheader ("content-type", "text/xml ");
Http_request.send (content );
   
If (navigator. useragent. indexof ("firefox")> = 0)
  {
If (callback = 1)
Http_request.onreadystatechange = populateclass1 ();
Else if (callback = 2)
Http_request.onreadystatechange = populateclass2 ();
  }
}
Initialize the drop-down box and call the send_request method. These two functions are called directly in the drop-down box.
Function getregiontwo (oneid)
{
If (oneid! = '0 ')
  {
Document. getelementbyid ("region_selregionthree"). options. length = 1;
Var url = "controls/getregionhandler. ashx? Type = regiontwo & oneid = "+ oneid;
   
If (navigator. useragent. indexof ("firefox") <0)
Send_request (url, null, populateclass1 );
Else
Send_request (url, null, 1 );
  }
Else
  {
Document. getelementbyid ("region_selregiontwo"). length = 1;
Document. getelementbyid ("region_selregiontwo"). selectedindex = 0;
Document. getelementbyid ("region_selregionthree"). length = 1;
Document. getelementbyid ("region_selregionthree"). selectedindex = 0;
  }
}

Function getregionthree (oneid, twoid)
{
If (oneid! = '0' & twoid! = '0 ')
  {
Var url = "controls/getregionhandler. ashx? Type = regionthree & oneid = "+ oneid +" & twoid = "+ twoid;
If (navigator. useragent. indexof ("firefox") <0)
Send_request (url, null, populateclass2 );
Else
Send_request (url, null, 2 );
  }
Else
  {
Document. getelementbyid ("region_selregionthree"). length = 1;
Document. getelementbyid ("region_selregiontwo"). selectedindex = 0;
  }
}

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