You can use this to prevent deletion of a folder:
BANano.TranspilerOptions.DoNotDeleteFolderOnCompilation("FullPathToTheFolder")
It is however strongly advised NOT to put the 'root' there, but use subfolders. Setting it on the root will prevent deletion of the whole project and this can give unexpected results, versioning problems and lots of very hard to debug bugs.
So for example if my Webapp has a subfolder /jsons
C:\myApp\Objects\MyApp\
C:\myApp\Objects\MyApp\scripts\
C:\myApp\Objects\MyApp\assets\
C:\myApp\Objects\MyApp\styles\
C:\myApp\Objects\MyApp\jsons\
I could add a line in AppStart:
BANano.TranspilerOptions.DoNotDeleteFolderOnCompilation(File.Combine(File.DirApp, "MyApp/jsons/")
Alwaysbusy