Beginning Web Development, Silverlight, and ASP.NET AJAX

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CHAPTER 16 ■ PROGRAMMING SILVERLIGHT WITH XAML AND JAVASCRIPT
In this case, the txtBlock var is set to a reference to the TextBlock called txt. Now that
you have this, you can just change its Text property using the standard dot syntax.
In addition to the dot syntax, you can use the setValue and getValue methods on the
object. When using attached properties, you have to use this methodology. Here’s an
example:
txtBlock.setValue("Canvas.Top",200);
Using Common Methods
There are a number of methods that all XAML elements have in common. We’ll first summarize
them, and then look into the more important methods that exist on specific
controls.
The AddEventListener and RemoveEventListener Methods
One of the nice things about Silverlight is how it separates the design and developer artifacts
to allow them to work together more efficiently. You can specify an event handler for
an item by using a XAML attribute to define the name of the function that will have the
code to run in response to the event. For example, you can use the syntax MouseLeftButton
= "handleClick" to declare that you want to use the JavaScript function handleClick when
this element is clicked. The drawback with this is that it involves a developer editing the
XAML from the designer directly, thus breaking the separation.
Silverlight allows you to avoid this by using AddEventListener to declare the handler at
runtime. You’ll typically do this as part of Silverlight loading. Your handler function will
take two parameters: sender, which contains a reference to the control that the event was
raised on; and args, which contains any arguments associated with the event. Here’s an
example:
function handleLoad(control, context, sender)
{
var txtBlock=control.content.findName("txt");
txtBlock.addEventListener("mouseLeftButtonDown", handleTxtClick);
}
function handleTxtClick(sender,args)
{
alert("You clicked the Text Block");
}