如何获取web应用根目录?

它可能看起来太过火了,但这是我使用的助手例程。我还没有遇到任何麻烦。

public class UrlHelper
{
    public static string ApplicationBaseUrl()
    {
        string port = HttpContext.Current.Request.ServerVariables["SERVER_PORT"];

        if (port == null || port == "80" || port == "443")
            port = "";
        else
            port = ":" + port;

        string protocol = HttpContext.Current.Request.ServerVariables["SERVER_PORT_SECURE"];

        if (protocol == null || protocol == "0")
            protocol = "http://";
        else
            protocol = "https://";

        return protocol + HttpContext.Current.Request.ServerVariables["SERVER_NAME"] + port +
               HttpContext.Current.Request.ApplicationPath;
    }
}