获取根目录的URL例如http://localhost:51898

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; 
}