关于一个独立主格结构的句子
If i had been invited to your birthday party,i would have bought a birthday gift for you.
若我想把这句话写成独立主格结构 那么if引导的从句该如何改写?
我是这么写的：Having been invited to your birthday party,i would have bought a birthday gift for you.可别人说这么不对.主句和从句的主语都是I 我把它省略了 用了一个ing代替了连词与主语 错在哪里了.
希望有人能帮忙改下这句话.