可以更新约会，但不能更新约会的方式.这是重要的:

It is possible to update an appointment, but not the way you did it. Here's what's important:

• METHOD应该为REQUEST-PUBLISH事件将不会更新，它将被一次又一次地添加. REQUEST会议请求的行为有所不同，甚至会在用户批准之前更新现有会议.我会注意到，如果事件已经是发布"类型的，则无法更新(至少据我所知).
• 您必须使用完全相同的UID.
• DTSTAMP应该大于现有的日期戳(如果是动态创建，应该可以)
• 包括一个ORGANIZER-Outlook可能不允许人们在没有会议的情况下接受会议(虽然不相关，但很重要).

• METHOD should be REQUEST - a PUBLISH event will not update, it will be added again and again. REQUEST meeting requests behave differently, and will update the existing meeting even before the user approves it. I'd note that if the events are already of type Publish, they cannot be updated (at least to my knowledge).
• You must use the exact same UID.
• DTSTAMP should be bigger than the existing date stamp (this should be OK if you're creating it dynamically)
• Include an ORGANIZER - Outlook may not allow people to accept the meeting without it (not really related, but important).

我的博客对此有一个 partial 总结-

I have a partial summery of this in my blog - Sending Meeting Requests to Outlook via ASP.NET Mail Message, though it's missing sending the approval to the organizer, and time zones (which are very important, so I've heard).

另请参阅: RFC 2446-iTIP ，搜索 1.3 ITIP部分角色和交易