The’UserConrol’ is the parent xaml tag of a Silverlight page. All other tags are authored under UserControl tag. Developers are given a facility to implement new custom controls and create re-usable user controls. This makes the use of XAML file easy for composing a control’s UI and easy to implement.
The following code snippet resembles the UserControl tag.
<UserControl x:Class="SilverlightApplication2.MainPage" Width="400" Height="300">
<Grid x:Name="LayoutRoot" Background="Green">
</Grid>
</UserControl>