asp.net 获取网站根地址

 public static string GetSiteRoot()
         {
             string port = System.Web.HttpContext.Current.Request.ServerVariables["SERVER_PORT"];
             if (port == null || port == "" || port == "")
             {
                 port = "";
             }
             else
             {
                 port = ":" + port;
             }
             string protocol = System.Web.HttpContext.Current.Request.ServerVariables["SERVER_PORT_SECURE"];
             if (protocol == null || protocol == "")
             {
                 protocol = "http://";
             }
             else
             {
                 protocol = "https://";
             }
             string sOut = protocol + System.Web.HttpContext.Current.Request.ServerVariables["SERVER_NAME"] + port + System.Web.HttpContext.Current.Request.ApplicationPath;
             if (sOut.EndsWith("/"))
             {
                 sOut = sOut.Substring(, sOut.Length - );
             }
             return sOut;
         }