Application resources utilize the style elements for supporting the forms. The App.xaml file could be used to contain an application resource XML construct. Each style’s target type is set to the control that needs the style.
App.xaml:
<Application.Resource>
<Style x:Key="MyBorder" TargetType="Border">
<setter property="width" value="3">
</style>
Page.xaml:
<Border Style="{StaticResource MyBorder}">
...
</Border>