public class MainWindowSettings

{

    public static void Initialize()

    {

        if(!Application.Current.IsRunningOutOfBrowser)

            return;

        if (!Application.Current.HasElevatedPermissions)

            return;

        Initialize(Application.Current.MainWindow);

    }

    private static void Initialize(Window mainWindow)

    {

        var appSettings = new ApplicationSettings();

        var settings = appSettings.Read<Settings>(Settings.Key, null);

        if (settings != null)

        {

            mainWindow.WindowState = settings.WindowState;

            if (settings.WindowState != WindowState.Maximized)

            {

                mainWindow.Height = settings.Height;

                mainWindow.Width = settings.Width;

                mainWindow.Top = settings.Top;

                mainWindow.Left = settings.Left;

            }

        }

        mainWindow.Closing += (sender, args) =>

        {

            var windowSettings = new Settings

            {

                Height = mainWindow.Height,

                Width = mainWindow.Width,

                Top =  mainWindow.Top,

                Left = mainWindow.Left,

                WindowState = mainWindow.WindowState

            };

            new ApplicationSettings().Write(Settings.Key, windowSettings);

        };

    }

    public class Settings

    {

        public const string Key = "MainWindowSettings";

        public Settings()

        {

            WindowState = WindowState.Normal;

        }

        public double Width { get; set; }

        public double Height { get; set; }

        public double Top { get; set; }

        public double Left { get; set; }

        public WindowState WindowState { get; set; }

    }

}