What is ResourceDictionary?
ResourceDictionary is used to define the XAML Resources, which can be reused more than once throughout the Xamarin.Forms application.
* Xaml Resources are the definition of objects which can be used more than once.
* ResourceDictionary allows all the resource objects declared at one place.
* We can define Styles, ControlTemplates, DataTemplates, Colors, and Converters into the ResourceDictionary.
* In XAML, resources can be accessed at the Element level (inside specific element), Page (inside page) level or Application Level (inside App.Xaml).
