I can create an appointment using Microsoft.Xrm.Sdk powershell although I'm not sure how to add attendees. It is not possible to create activityparty records via powershell. The requiredattendees field is available on the appointment entity, it has a type of Microsoft.Xrm.Sdk.EntityCollection. I need to create an EntityCollection containing contacts and/or users and then associate that collection with the activity.
Is anyone aware of how to create the EntityCollection?