URL Rewrite

1. 原理：

http://www.cnblogs.com/jeffreyzhao/archive/2008/01/12/url-rewrite-1.html 

2. url解析：

For example, if a request was made for this URL: http://www.mysite.com/content/default.aspx?tabid=2&subtabid=3, and a rewrite rule was defined on the site level then:
　　The rule pattern gets the URL string content/default.aspx as an input
　　The QUERY_STRING server variable contains tabid=2&subtabid=3.
　　The HTTP_HOST server variable contains www.mysite.com.
　　The SERVER_PORT server variable contains 80.
　　The SERVER_PORT_SECURE server variable contains 0 and HTTPS contains OFF.
　　The REQUEST_URI server variable contains /default.aspx?tabid=2&subtabid=3
from: http://www.iis.net/learn/extensions/url-rewrite-module/url-rewrite-module-configuration-reference#UsingServerVars

3. Url Rewrite指南（很全很全）：

http://learn.iis.net/page.aspx/461/creating-rewrite-rules-for-the-url-rewrite-module/ 

http://learn.iis.net/page.aspx/465/url-rewrite-module-configuration-reference/

4. 获取全部Server Variables ：

            var collection = System.Web.HttpContext.Current.Request.ServerVariables;
            var str = new StringBuilder();
            foreach (var key in collection.AllKeys)
            {
                str.Append(String.Format("<b>{0}</b><font color=\"red\"> :</font> {1}<br />", key, collection[key]));
            }