/// <summary>
        /// Check if there is a user loaded in SavaAndLoad
        /// Display the corresponding Page.Content
        /// </summary>
        private void CheckUser()
        {
            // read user.json
            user = SaveAndLoad.GetUser();

            bool hasUser = (user != null);

            if (hasUser)
            {
                user_name.Text             = user.Name;
                user_logged.IsVisible      = true;
                user_newORloggin.IsVisible = false;
            }
            else
            {
                user_name.Text             = null;
                user_logged.IsVisible      = false;
                user_newORloggin.IsVisible = true;
            }
        }