(1)Thank you for helping me.It's my pleasure(2)Would you please open the widow?With pleasure.可见It's my pleasure是回答别人的感谢的，可译为“那是我应该做的”，而whth pleasure是回答别人的请求的，可译为“好的，乐意效劳”。第一句是谢谢的意思。
It's my pleasure或者it's省略 直接说 my pleasure表示 ：不用谢.用于回答别人感谢----thank you for your help.----(It's )my pleasure.with pleasure表示：很荣幸,很乐意.用于回答别人请求.----i know little about tennis .would you please teach me ?----with pleasure.我个人觉得：第一句话比较正式第二句话比较随便这粮两句一个意思
