Button derives from Control but it also derives from ContentControl, which is the class that provides the button’s Content property. You can pull out the Content property as a property element:
<Button> <Button.Content> </Button.Content> </Button>
But oddly enough you can’t put text in there:
<!-- Doesn't work! --> <Button> <Button.Content> Click this button! </Button.Content> </Button>
There’s nothing ostensibly wrong with that syntax but Silverlight doesn’t allow it. If you really want to do something like this you’ll need an XML namespace declaration for the System namespace:
You can then put the string between tags that explicitly tell the XAML parser than the string is ...