Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 12 ■ AJAX EXTENSIONS FOR ASP.NET 289
Migrating ASP.NET to AJAX
One of the nicest things about ASP.NET AJAX is the fact that the UpdatePanel control
can be used to add AJAX functionality to an existing ASP.NET application. This is simply
achieved by wrapping the relevant controls with an UpdatePanel.
Consider the following example. Add a new web form to your application and call it
AddWithUpdatePanel.aspx. On this form, add a couple of text boxes, a button, and a label,
and call them txtA, txtB, btnAdd, and lblAns, respectively. The source of your page should
look like this:
Untitled Page
 
Double-click the button to add an event handler, and add the following code to it:
protected void btnAdd_Click(object sender, EventArgs e)
{
int a = Convert.ToInt16(txtA.Text);
int b = Convert.ToInt16(txtB.Text);