路径问题最后的出来的路径不对

Question

string str = Server.MapPath("~/manage/upload/");

                System.IO.Directory.CreateDirectory(str + "/" + username + "/");

                File1.PostedFile.SaveAs(str + "/" + username + "/" + username + newname);

                string strr = Path.GetFileName(str + "/" + username + "/" + username + newname);//有错误

                string strfile = Server.MapPath(strr);

                super.Supervise_way = strfile;

取出的路径不对

老是出现错误