public ThemeManager(bool useWinSysAccent, bool useWinDefFont, bool includeWindowsTitleBar) { UseSegoeUIOnWindows = useWinDefFont; UseSystemAccentOnWindows = useWinSysAccent; IncludeWindowsTitleBarInThemeChange = includeWindowsTitleBar; _isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows); if (_isWindows) { Win32Interop.OSVERSIONINFOEX osInfo = new Win32Interop.OSVERSIONINFOEX { OSVersionInfoSize = Marshal.SizeOf(typeof(Win32Interop.OSVERSIONINFOEX)) }; Win32Interop.RtlGetVersion(ref osInfo); bool useDark = Win32Interop.GetSystemTheme(osInfo); PreferredTheme = useDark ? FluentThemeMode.Dark : FluentThemeMode.Light; } else { PreferredTheme = FluentThemeMode.Light; } }