Beginning Ajax With ASP.NET (2006).pdf

Next listed in the following code blocks are the JavaScript functions that accompany the page listing.
The first function is a generic function to simply create an XMLHttpRequest object that you can use:
Untitled Page
The XMLHttpRequest Object
// A “global” variable that is our XMLHttpRequest object reference.
var xmlHttpObj = CreateXmlHttpRequestObject();
The next function is what is called when the document first loads and deals with loading the customer
data from the server using the XMLHttpRequest object:
// Function to load the customer selection data into the drop list control
function LoadCustomers()
{
if (xmlHttpObj)
{
// We want this request synchronous
xmlHttpObj.open(“GET”,”http:// “ + location.host +
“/XmlHttp_Chap4/DataFile.xml”, false);
// Execute the request
xmlHttpObj.send(null);
// If the request was ok (ie. equal to a Http Status code of 200)
if (xmlHttpObj.status == 200)
{
var xmlDoc = xmlHttpObj.responseXML;
// Our list of nodes selected using the X Path argument
//var nodes = xmlDoc.selectNodes(“//Customers/Customer”);
var nodes = xmlDoc.selectNodes(“//Customers/Customer/Lastname/text()”);
// Obtain a reference to the drop list control.
var ctrl = document.getElementById(“ddlCustomers”);
for (var i=0; i < nodes.length; i++)
{
// Get the lastname element from our XML data document
var lastName = nodes[i].nodeValue;
// Create a new node.
var htmlCode = document.createElement(‘option’);
// Add the new node to our drop list
ctrl.options.add(htmlCode);
// Set the display text and value;
htmlCode.text = lastName;
htmlCode.value = lastName;
}
} else
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