title: How to efficiently retrieve an Appoinment Ocurrence's index in EWS
body: <p><code>Appointment.BindToOcurrence</code> takes the following arguments:</p>
  
  <p><code>service</code>, <code>ItemId</code>, and <code>Index</code>.</p>
  
  <p>However, there doesn't seem to be an efficient way to get said index, given an occurrence, without looping over every single item in the series.</p>
  
  <p>If I want to store some information that will allow me to retrieve a specific event in the series, regardless of what account is viewing the appointment, I can store <code>CleanGlobalObjectId</code> and ideally part of the recurring data, however, all you get is the ItemID (which is not global to all users), the Start, End. </p>
  
  <p>How do I retrieve the index of a recurring item without doing a loop?</p>