如何为asp.net控件添加可以保存状态的属性

 /// <summary>
    /// 扩展textbox的属性，使其增加几个信息字段，方便数据操作
    /// </summary>
    public class TextBoxExtend:TextBox
    {
        public string Argument_1
        {
            get { string s = (string)ViewState["Argument_1"];
            return ((s == null) ? string.Empty : s);
            }
            set { ViewState["Argument_1"] = value; }
        }

        public string Argument_2
        {
            get
            {
                string s = (string)ViewState["Argument_2"];
                return ((s == null) ? string.Empty : s);
            }
            set { ViewState["Argument_2"] = value; }
        }

        public string Argument_3
        {
            get
            {
                string s = (string)ViewState["Argument_3"];
                return ((s == null) ? string.Empty : s);
            }
            set { ViewState["Argument_3"] = value; }
        }
    }