Here I assumed that you dont know how exactly basic style is incorporated in xaml. So first of all look for(i mean search in whole solution and where exactly style is defined) two styles in BasicTextStyle and BasicContentStyle and see where exactly it is located.It should be somewhere in other xaml(which is your ResourceDictionary) and now go to app.xaml file and see that it is present in ResourceDictionaries section. If not present then add this particular file in Resource Dictionary and then try to Rerun again.
you can also do this in other by adding resource Dictionary Reference on the same xaml as described below
Using a Resource Dictionary in WPF[
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