title: Replace Existing Outlook Calendar Appointment
body: <p>I'm doing some work with an icalndar appointment generation; this would allow a delegate to view an event's website and click on a link provided to add an appointment to their calendar.</p>
  
  <p>I have a working assembly that will generate an ics formatted output (as either a physical file or a Stream) based on a known set of information (start date, end date, title etc.).</p>
  
  <p>An example of the output I generate for a calendar appointment is the following:</p>
  
  <pre><code>BEGIN:VCALENDAR
  PRODID:-//Microsoft Corporation//Outlook 12.0 MIMEDIR//EN
  VERSION:2.0
  METHOD:PUBLISH
  X-MS-OLK-FORCEINSPECTOROPEN:TRUE
  BEGIN:VEVENT
  CLASS:PUBLIC
  CREATED:20110210T124703Z
  DESCRIPTION:Anything Else\n\nHopefully some useful information would be written here\n
  DTEND:20110212T100000Z
  DTSTAMP:20110210T124600Z
  DTSTART:20110212T090000Z
  LAST-MODIFIED:20110210T124703Z
  LOCATION:Dummy Location
  PRIORITY:5
  SEQUENCE:0
  SUMMARY;LANGUAGE=en-us:Dummy Meeting
  TRANSP:OPAQUE
  UID:040000008200E00074C5B7101A82E00800000000B0D1061C57C8CB01000000000000000
      010000000281117EDC1194242B64F0247C54DB401
  X-ALT-DESC;FMTTYPE=text/html:&lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"&gt;\n&lt;HTML&gt;\n&lt;HEAD&gt;\n&lt;META HTTP-EQUIV="Content-Type" CONTENT="text/html\;    charset=Windows-1252"&gt;\n&lt;META NAME="Generator" CONTENT="MS Exchange Server
   version 6.5.7654.12"&gt;\n&lt;TITLE&gt;Dummy Meeting&lt;/TITLE&gt;\n&lt;/HEAD&gt;\n&lt;BODY&gt;\n&lt;!-
  - Converted from text/plain format --&gt;\n\n&lt;P&gt;&lt;FONT SIZE=2&gt;&amp;lt\;h1&amp;gt\;Anyt
  hing Else&amp;lt\;/h1&amp;gt\;&amp;lt\;p&amp;gt\;Hopefully some useful information would b
  e written here&amp;lt\;/p&amp;gt\;&lt;BR&gt;\n&lt;/FONT&gt;\n&lt;/P&gt;\n\n&lt;/BODY&gt;\n&lt;/HTML&gt;
  X-MICROSOFT-CDO-BUSYSTATUS:BUSY
  X-MICROSOFT-CDO-IMPORTANCE:1
  END:VEVENT
  END:VCALENDAR
  </code></pre>
  
  <p>What I have been asked is; is it possible to change the appointment, but the next time someone requests the reminder it will detect the appointment as already existing in their calendar and update it instead of creating a new entry?</p>
  
  <p>So I am trying to find if it is possible to overwrite an existing calendar appointment.</p>
  
  <p>I noticed that there was a UID value, I have tried keeping this value the same, but it doesnt appear to provide a link between the calendar appointments.</p>
  
  <p>Is it possible that the Save and Close action on the calendar appointment generates a new UID so there is no longer a link?</p>
  
  <p>What else can I try?</p>