// ########## STORES THE XMLHTTP OBJECT
var xmlhttp = createxmlhttp();

// ########## CREATES AN XMLHTTP OBJECT
function createxmlhttp() {
	var xmlhttp;

  	if(window.ActiveXObject) { // INTERNET EXPLORER
    	try {
      		xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    	} catch (e) {
      		xmlhttp = false;
    	}
  	} else { // OTHER BROWSERS
    	try {
      		xmlhttp = new XMLHttpRequest();
   		} catch (f) {
      		xmlhttp = false;
    	}
  	}
    
  	if (!xmlhttp) { // RETURN THE OBJECT OR DISPLAY ERROR
		alert('there was an error creating the xmlhttp object');
  	} else {
    	return xmlhttp;
	}
}

// ########## MAKE AN ASYNCHRONOUS CALL USING THE XMLHTTP OBJECT
// ########## THE VARIABLE STR BEING THE TEXT ALREADY ENTERED
function searchforwords(str) {
	try {
  		// PROCEED ONLY IF OBJECT IS NOT BUSY
		if (xmlhttp.readyState === 4 || xmlhttp.readyState === 0) {
    		// EXECUTE THE PAGE ON THE SERVER AND PASS QUERYSTRING
    		xmlhttp.open("POST", "autocomplete.aspx?text=" + str, true);
    		// DEFINE METHOD TO HANDLE THE RESPONSE
    		xmlhttp.onreadystatechange = handleresponse;
    		// MAKE CALL
    		xmlhttp.send(null);
						
  		} else {
    		// IF CONNECTION IS BUSY, WAIT AND RETRY
    		setTimeout('searchforwords("' + str + '")', 1000);
  		}
  	} catch(e) {
  		alert('ERROR: ' + e);
  	}
}

// ########## EXECUTED WHEN MESSAGE IS RECIEVED
function handleresponse() {
	try {
		
  		// MOVE FORWARD IF TRANSACTION COMPLETE
  		if (xmlhttp.readyState == 4) {
			
    		// STATUS OF 200 INDICATES COMPLETED CORRECTLY
			if (xmlhttp.status == 200) {
				
				// WILL HOLD THE XML DOCUMENT
				var xmldoc;
				if (window.ActiveXObject) { // INTERNET EXPLORER
  					xmldoc = new ActiveXObject("Microsoft.XMLDOM");
  					xmldoc.async = "false";
  					xmldoc.loadXML(xmlhttp.responseText);
  				} else { // OTHER BROWSERS
  					var parser = new DOMParser();
  					xmldoc = parser.parseFromString(xmlhttp.responseText, "text/xml");
  				}
				
				// PARSE EACH RESULT
				var res = xmldoc.getElementsByTagName('result');
				for(var i = 0; i < res.length; i ++) {
				    alert(res[i].childNodes[0].nodeValue); // DO SOMETHING WITH THIS VALUE
				}
				
    		} else { // STATUS OTHER THAN 200 IS AN ERROR
				alert('there was an error recieving the message');
    		}
  		}
  	} catch(e) {
  		alert('there was an error contacting the server');
  	}
}

Imports System.Xml

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim xmldoc As XmlTextWriter

        ' SETUP THE PAGE
        Response.Clear()
        Response.ContentType = "text/xml"

        ' SETUP THE XML DECLARATION
        xmldoc = New XmlTextWriter(Response.OutputStream, System.Text.Encoding.UTF8)
        xmldoc.WriteStartDocument(True)
        xmldoc.WriteStartElement("root")

        findwords(xmldoc)
        xmldoc.WriteEndElement()
        xmldoc.WriteEndDocument()
        xmldoc.Close()
        Response.End()
    End Sub

    ' ########## FINDS MATCHING WORDS IN DATABASE AND PRINTS THEM TO THE XML WRITER
    Private Function findwords(ByVal xmldoc As XmlWriter) As String
        ' USE 'Request.Querystring("txt")' TO RETURN THE VARIABLE PASSED FROM THE HTML PAGE
        ' PERFORM DATABASE QUERY HERE AND RETURN VALUES
        ' THEN LOOP THROUGH THE VALUES AND PRINT THEM TO THE XML USING THE METHOD BELOW
                xmldoc.WriteElementString("result", DATABASE VALUE)
    End Function

<INPUT type="text" name="searchtext" onkeypress="searchforwords(this.value)" />