获取网站根目录的url

    public static string GetRootURI()
    {
        string AppPath = "";
        HttpContext HttpCurrent = HttpContext.Current;
        HttpRequest Req;
        if (HttpCurrent != null)
        {
            Req = HttpCurrent.Request;

            string UrlAuthority = Req.Url.GetLeftPart(UriPartial.Authority);
            if (Req.ApplicationPath == null || Req.ApplicationPath == "/")
                //直接安装在   Web   站点  
                AppPath = UrlAuthority;
            else
                //安装在虚拟子目录下  
                AppPath = UrlAuthority + Req.ApplicationPath;
        }
        return AppPath;
    }