output.AddAttribute("id", "2");
            output.AddAttribute("type", "checkbox");
            output.AddAttribute("value", "测试2");
            output.AddAttribute("onclick", "javascript:doClick2();");
            output.RenderBeginTag(HtmlTextWriterTag.Input);
            output.RenderEndTag();

            base.RenderContents(output);
        }
    }
}

大家可以试试