How to have diffrent Styles.xaml and Colors.xaml and use BuildConfiguration to use the right one

[albertruff]

I create a whitelabeling app and need aplly diffrent Ressources for diffrent Customers befor the App compiles. For App-Icon, Fonts, Images it is not complicated. I created diffrent Build Configs and Item Groups that have Conditions with the right ressource path for the customer. The only think, that is not spezified in the .csproj, is the Styles Files-Location. I tried diffrent approaches to set a custom location, but I dont have found the right solution. The last thing I tried, is a prebuildscript that copy the Style-Files in the Ressources/Styles directory. But this don't work properly. Can somone help me with a solution?