function CallTemplate()
			{
			
			  //alert(document.getElementById('cmbAssignTo_cmbSimple').value);
					
			       var objDd=  document.getElementById('ddlmenu')
			       
					var strValue = objDd.options[objDd.selectedIndex].value;					
					
					//Create XMLHttpRequest object:'request'
						
						CreateXmlHttpRequestObject();
						
						//Build the required Query string
						var sPass=1;
						
						var retrieveParam = 'id='+ strValue;
						
						var retrieveURL = "AJAX.aspx";
						var url = retrieveURL + '?' + retrieveParam;
						
						request.open('GET',url,true);
						
						request.onreadystatechange = CheckTemplate;
					
						request.send(null);	
			}
				 
			function CheckTemplate()
			{
				document.getElementById("ddlsubmenu").innerText="";
			    if(request.readyState == 4 || request.readyState == 'complete')
				{
					if(request.status == 200)
					{	
							var opt=document.createElement("option");
							opt.value="-1"; 
							opt.text="----select subcategory---";
							document.getElementById("ddlsubmenu").add(opt); 
							var DdVisitTemp = document.getElementById("ddlmenu");
							
							var rootFile = request.responseXML.documentElement;
						  
							var Id = rootFile.getElementsByTagName('Id');
							
							var Name = rootFile.getElementsByTagName('Name');
							
							  if(Id.length > 0 || Name.length > 0)
						      {
						
								for(var i=0;i								{
									
									   if(Name.length > 0)
									   {
										 var opt=document.createElement("option");
										
										opt.value=Id[i].text; 
											
										opt.text=Name[i].text;
										
										document.getElementById("ddlsubmenu").add(opt); 
										
									  }
									
								}
								
							}
							  
					}//	inner IF		
			
			} // Outer IF
			
		}
		
		function CreateXmlHttpRequestObject()
			{
				try
				{
					request = new XMLHttpRequest();
				}
				catch(nething)
				{
					try
					{
						request = new ActiveXObject('Msxml2.XMLHTTP');
					}
					catch(othr)
					{
						try
						{
							request = new ActiveXObject('Microsoft.XMLHTTP');
						}
						catch(err)
						{
							request = false;
						}
					}
				}
				if(!request)
				{
					alert("Error initializing XMLHttpRequest object!");
				}
			}




code for ajax page i.e ajax.aspx




private void Page_Load(object sender, System.EventArgs e)
		{
					
						string id=string.Empty ;
			System.Text.StringBuilder strXml;
			string passedValue = Request.QueryString["id"];

						string strFill=" select  PK_PRIMARY_KEY,TITLE_SUBMENU from SUBJECT_SUBMENU where FK_SUBJECTMENU_ID = '" + id + "' ";
			
			DataTable dttemp= con.connectiondatatable(strFill);
			


			int j=dttemp.Rows.Count; 
			strXml = new System.Text.StringBuilder (); 
			strXml.Append("");
			XmlDocument xTemplate = new XmlDocument();
			xTemplate.LoadXml(strXml.ToString());

			Response.ContentType = "text/xml";
			Response.CacheControl = "No-cache";
			xTemplate.Save(Response.OutputStream);
			
			// Put user code to initialize the page here
		}

<%@ Page language="c#" Codebehind="AJAX.aspx.cs" AutoEventWireup="false" Inherits="KnowledgeSharing.AJAX" %>