Hello,
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All the XAML templates and resources are defined in the Generic.xaml
file. There are two ways you could check the file.
1) You could check the Page you are using, it will predefine a background property
using a theme brush. You could select the Theme brush and Press F12, then you will jump to the definition of the theme brush which is exactly the Generic.xaml
file.
2) You could directly go to the C:(Program Files)\Windows Kits\10\DesignTime\CommonConfiguration\Neutral\UAP\<SDK version>\Generic folder from a Windows Software Development Kit (SDK) installation. Then you could find the Generic.xaml
file.
Thank you.
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