HttpContext.Current.Request.Url.ToString() 并不可靠。
如果当前URL为
http://localhost/search.aspx?user=http://csharp.xdowns.com&tag=%BC%BC%CA%F5
通过HttpContext.Current.Request.Url.ToString()获取到的却是
http://localhost/search.aspxuser=http://csharp.xdowns.com&tag=¼¼Êõ
正确的方法是：HttpContext.Current.Request.Url.PathAndQuery

通过ASP.NET获取URL地址方法
如果测试的url地址是http://www.test.com/testweb/default.aspx, 结果如下：
Request.ApplicationPath: /testweb
Request.CurrentExecutionFilePath: /testweb/default.aspx
Request.FilePath: /testweb/default.aspx
Request.Path: /testweb/default.aspx
Request.PhysicalApplicationPath: E:\WWW\testwebRequest.PhysicalPath:
Request.PhysicalPath: E:\WWW\testweb\default.aspx
Request.RawUrl: /testweb/default.aspx
Request.Url.AbsolutePath: /testweb/default.aspx
Request.Url.AbsoluteUrl: http://www.test.com/testweb/default.aspx
Request.Url.Host: www.test.com
Request.Url.LocalPath: /testweb/default.aspx