c＃dll将错误返回给调用应用程序的好方法是什么？

i'm writing a dll which is a wrapper to a access database. and i'm pretty new to c# in general as my background is in web development LAMP with perl, i'm not sure what's a good way to return error to a calling app in case they pass the wrong parameters to my functions or what not.i'm writing a dll which is a wrapper to a acces