Hide/Show controls with AJAX

protected void Page_Load(object sender, EventArgs e)
{
    ScriptManager1.RegisterAsyncPostBackControl(Button1);


    if (!IsPostBack)
    {

        Visibility = true;
    }

    UpdatePanel_1.Visible = !Visibility;
    UpdatePanel_2.Visible = Visibility;

    Visibility = !Visibility;
}


protected void Button1_Click(object sender, EventArgs e)
{
        if (Panel1.Visible)
                 UpdatePanel_1.Update();
}

protected bool Visibility
{
    get
    {
        return (bool)(ViewState["Visibility"] ?? true);
    }
    set
    {
        ViewState["Visibility"] = value;
    }
}