在URL重写后，form标记中的Action值也用虚拟地址

首先建立/App_Browsers/Form.broswer文件，其内容为：

<browsers>
    <browser refID="Default">
        <controlAdapters>
            <adapter controlType="System.Web.UI.HtmlControls.HtmlForm"
                        adapterType="FormRewriterControlAdapter" />
        </controlAdapters>
    </browser>

</browsers>
再建立FormRewriterControlAdapter类：

    public class FormRewriterControlAdapter : System.Web.UI.Adapters.ControlAdapter
    {
        protected override void Render(HtmlTextWriter writer)
        {

            if (writer is System.Web.UI.Html32TextWriter)
            {
                writer = new FormFixerHtml32TextWriter(writer.InnerWriter);
            }
            else
            {
                writer = new FormFixerHtmlTextWriter(writer.InnerWriter);
            }

            base.Render(writer);
        }
    }

    #region FormFixerHtml32TextWriter
    internal class FormFixerHtml32TextWriter : System.Web.UI.Html32TextWriter
    {
        private string _url; // 假的URL

        internal FormFixerHtml32TextWriter(TextWriter writer)
            : base(writer)
        {
            _url = HttpContext.Current.Request.RawUrl;
        }

        public override void WriteAttribute(string name, string value, bool encode)
        {
            // 如果当前输出的属性为form标记的action属性，则将其值替换为重写后的虚假URL
            if (_url != null && string.Compare(name, "action", true) == 0)
            {
                value = _url;
            }
            base.WriteAttribute(name, value, encode);
        }
    }
    #endregion

    #region FormFixerHtmlTextWriter
    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 encode)
        {
            if (_url != null && string.Compare(name, "action", true) == 0)
            {
                value = _url;
            }

            base.WriteAttribute(name, value, encode);
        }
    }
    #endregion