if (User.IsInRole("Administrators")) {
        WebPartManager1.DisplayMode = WebPartManager.EditDisplayMode();
        WebPartManager1.DisplayMode = WebPartManager.DesignDisplayMode();
    }
    else if (User.IsInRole("NormalUsers")) {
        WebPartManager1.DisplayMode = WebPartManager.BrowseDisplayMode();
    }
    else {
        Response.Write("Invalid user");
    }