自定义控件，如何输出<input type="hidden" />的input

            //AreaId隐藏域
            writer.AddAttribute(HtmlTextWriterAttribute.Name, "AreaId");
            writer.AddAttribute(HtmlTextWriterAttribute.Id, "AreaId");
            writer.AddAttribute(HtmlTextWriterAttribute.Value, string.IsNullOrEmpty(this.Id) ? this.ParentId : this.Id);
            writer.RenderBeginTag(HtmlTextWriterTag.Input);
            writer.RenderEndTag();

这段输出结果：<input name="AreaId" id="AreaId" value="f5deb16f-df87-421e-acc6-515bde3a6f8d" />
我想给它加个属性type="hidden"怎么修改上面的C#代码？谢谢。
[解决办法]
writer.AddAttribute(HtmlTextWriterAttribute.Type, "hidden");