英语作文中《邀请函》的常用句式包括：
I am writing to invite you to...
例句：I am writing to invite you to my graduation ceremony.
翻译：我写信是为了邀请您参加我的毕业典礼。
It would be my pleasure to...
例句：It would be my pleasure to have you at my birthday party.
翻译：能让您参加我的生日聚会是我的荣幸。
I would like to invite you to...
例句：I would like to invite you to our school's annual talent show.
翻译：我想邀请您参加我们学校的年度才艺表演。
I am pleased to invite you to participate in...
例句：I am pleased to invite you to attend our annual conference.
翻译：我非常高兴邀请您参加我们的年度会议。
It is my honor to invite you to...
例句：It is my honor to invite you to the opening ceremony of our new library.
翻译：非常荣幸地邀请您参加我们新图书馆的开幕式。
We’re throwing a surprise party for... We’d like to invite you to...
例句：We’re throwing a surprise party for our friend's birthday, and we’d like to invite you to join us.
翻译：我们将为朋友的生日举办惊喜派对，我们想邀请您参加。
I wonder if you would like to come to...
例句：I wonder if you would like to come to our picnic this weekend.
翻译：我想知道您这个周末是否愿意来参加我们的野餐。
We are having/planning...on...（date） and we feel it would be a great idea if you can join us.
例句：We are having a charity fundraiser on Saturday, and we feel it would be a great idea if you can join us.
翻译：我们将于本周六举行慈善募捐活动，如果您能参加就太好了。
这些句式可以根据具体情境进行适当调整，以满足不同的邀请需求。希望这些信息对你有所帮助!