When you create a Silverlight project using Visual Studio, it creates a default XAML file called "MainPage.xaml". This is just a dummy start page created by Visual Studio, and it does not contain any visible UI elements. The default contents of the MainPage.xaml file looks like this:
<UserControl x:Class="SilverlightApplication1.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Width="400" Height="300">
<Grid x:Name="LayoutRoot" Background="White">
</Grid>
</UserControl>
