FileInfo fi = new FileInfo(HttpContext.Current.Server.MapPath(文件路径));
                    if (fi.Exists)
                    {
                        fi.MoveTo(HttpContext.Current.Server.MapPath(文件路径));
                    }

------解决方案--------------------
String path = "";// 旧文件路径
FileInfo fi = new FileInfo(path);
           if (fi.Exists)
           {
               fi.Delete(path);
           }

------解决方案--------------------
String path = "";// 旧文件路径  
FileInfo fi = new FileInfo(path);  
fi.Delete(path);  
删除是不会报异常的