从不继承System.Web.Ui.Page的对象获取文件的URL

I have an object that requires the URL of a file that resides in the root of my web application. If this was an object that inherited from System.Web.Ui.Page I would just use the httpRequest object. However because this object does not I am uncertain how to get this url. Depending on the calling object, the url will be either /something.htm or ~/something.htm I have an object that requires the URL of a fil