相对路径获取文件名

　　　　　　　string oldimage = "/upload/16-09-12/0e2e7006a021444780a6eb4d7e83167c.png";
            var index = oldimage.LastIndexOf("/");
            string newimage = "M" + oldimage.Substring(index + 1);       //缩略图
            string newpath = oldimage.Substring(0, index + 1);
            Console.WriteLine(index);
            Console.WriteLine(newpath);
            Console.WriteLine(newimage);
            Console.Read();