Styles
Styles allow you to provide a uniform look to your controls by putting all the details in one place.
You create a style for a control type (for example, Button), and that style is applied to all controls of that type (refer to the Explicit versus implicit styles section). You can also base a style on an existing style, extending or modifying the original.
Styles can be stored on the page that uses the control, or they can be stored at the application level. In either case, they are created inside ResourceDictionary, typically declared at the top of the file. To make them available at the application level, just put them in App.xaml.
Where to put your styles
If you are only going to use the styles on objects on a single page, it makes sense to put the styles in the resources of that page. If you want to be able to reuse these styles on multiple pages, then you will want them in App.xaml.
As an example, let’s return to the Login page and create ResourceDictionary...