Use folder name
To organize the views in your Visual Studio project using folders, you can use the qualifier name with the folder. To do so, name your folder like this: DeviceFamily-[qualifierString]. In this case, each XAML view file has the same name. Don't include the qualifier in the file name.
Here's an example, again for a file named MainPage.xaml. To create a view for mobile devices, create a folder named "DeviceFamily-Mobile", and place a XAML view named MainPage.xaml into it. To create a view for PC devices, create a folder named "DeviceFamily-Desktop", and place another XAML view named MainPage.xaml into it. Here's what the solution looks like in Visual Studio.