重写form里的action

        protected override void Render(System.Web.UI.HtmlTextWriter writer)
        {
            if(writer is System.Web.UI.Html32TextWriter)
            { writer=new FormFixerHtml32TextWriter(writer.InnerWriter);}
            else
            { writer=new FormFixerHtmlTextWriter(writer.InnerWriter);}
            base.Render(writer);
        }

        internal class FormFixerHtml32TextWriter:System.Web.UI.Html32TextWriter
        {
            private string _url;
            internal FormFixerHtml32TextWriter(TextWriter writer):base(writer)
            {
                _url=HttpContext.Current.Request.RawUrl;
            }
            public override void WriteAttribute(string name, string value, bool fEncode)
            {
                if(_url!=null&&string.Compare(name,"action",true)==0)
                {
                    value=_url;
                }
                base.WriteAttribute (name, value, fEncode);
            }
        }

        internal class FormFixerHtmlTextWriter:System.Web.UI.HtmlTextWriter
        {
            private string _url;
            internal FormFixerHtmlTextWriter(TextWriter writer):base(writer)
            {
                _url=HttpContext.Current.Request.RawUrl;
            }
            public override void WriteAttribute(string name, string value, bool fEncode)
            {
                if(_url!=null&& string.Compare(name,"action",true)==0)
                {
                    value=_url;
                }
                
                base.WriteAttribute (name, value, fEncode);
            }
        }