Note. I have no experience in silverlight, but in WPF I would do the following
, MyControl, UserControl, MyProperty. , ControlTemplate :
<UserControl.Template>
<ControlTemplate TargetType="{x:Type SomeNamespace:MyControl}">
<StackPanel>
<TextBlock Text="{TemplateBinding MyProperty}"/>
<ContentPresenter/>
</StackPanel>
</ControlTemplate>
</UserControl.Template>
{TemplateBinding} (OneWay!) , {Binding} DataContext.
ContentPresenter ControlTemplate , Content Property.