Set content schedule of content programmatically in Umbraco 11

I am trying to set the content schedule of a content in Umbraco 11 but I just can't get it to work. I can't find any reference relevant to Umbraco 11.

This is my code so far.

ContentSchedule sched = new ContentSchedule(doc.Key, "", expirationDate, ContentScheduleAction.Expire);

var contentScheduleCollection = new ContentScheduleCollection();
contentScheduleCollection.Add(sched);

contentService.Save(doc, contentSchedule: contentScheduleCollection);

This code runs with no errors but the schedule is not reflecting on the content.

Did you figure something out?

I found this mention, saying that you can also do

contentService.PersistContentSchedule(doc, contentScheduleCollection);

Source code for both the latest version and version 11 suggests that the method exists and should at least do something ...

To anyone who has encountered this, the solution is to not initialize ContentSchedule with the doc.key

Here's the working code.

ContentSchedule sched = new ContentSchedule("", expirationDate, ContentScheduleAction.Expire);

var contentScheduleCollection = new ContentScheduleCollection();
contentScheduleCollection.Add(sched);

contentService.Save(doc, contentSchedule: contentScheduleCollection);