Retrieve calendar items (Outlook API, WebDAV) displaying strange behaviour

Question

We are writing an MS Outlook plugin. To satisfy our business-logic, it should check all appointments between some dates. We are experiencing several problems with retrieving all items from calendars. We tried two options:

Outlook API. We use the standard logic that is described in MSDN - sort items by [Start], set IncludeRecurrences to True and run the Find\Restrict query over calendar items like here. It works fine in our test environment. However, in our customer's environment: For recurring appointments, start and end dates are set to the corresponding dates of a 'master appointment.' For example, in some room's calendar we have a weekly appointment that was created in January, and if we try to find all items in August, we get among others four items of this recurring appointment, but their start and end dates are set to January. But Outlook displays correct dates in the same calendar...
Very bad, but we still have WebDAV! We write a simple test application and try to query all items from the calendar using WebDAV. Of course, we didn't reinvent the wheel and just pasted the code from documentation. The previous problem is solved, but the next one arises: It doesn't return recurring items that were created more than approximately six months ago. I Haven't a clue - there are no parameters restricting 'old' items!

What is wrong? Are we missing something important?

Technical details: Exchange 2003, Outlook 2003-2010. Frankly speaking, the first error disappears if we turn on Cached Exchange Mode, but we can't do that.

var nameSpace = application.GetNamespace("MAPI");
var recepient = nameSpace.CreateRecipient(roomEMail);
recepient.Resolve();
var calendar = nameSpace.GetSharedDefaultFolder(recepient, OlDefaultFolders.olFolderCalendar);
var filter = string.Format("[Start]<'{1}' AND [End]>'{0}'",
  dateFrom.ToString("dd/MM/yyyy HH:mm", CultureInfo.InvariantCulture), dateTo.ToString("dd/MM/yyyy HH:mm", CultureInfo.InvariantCulture)
);
var allItems = calendar.Items;
allItems.Sort("[Start]");
allItems.IncludeRecurrences = true;
var _item = allItems.Find(filter);
while (_item != null) {
  AppointmentItem item = _item as AppointmentItem;
  if (item != null) {
    if (item.Subject != "some const")
      && (item.ResponseStatus != OlResponseStatus.olResponseDeclined)
      && (item.MeetingStatus != OlMeetingStatus.olMeetingReceivedAndCanceled 
      && item.MeetingStatus != OlMeetingStatus.olMeetingCanceled))
    {
      /* Here we copy item to our internal class.
       * We need: Subject, Start, End, Organizer, Recipients, MeetingStatus,
       * AllDayEvent, IsRecurring, RecurrentState, ResponseStatus,
       * GlobalAppointmentID */
    }
  }
  _item = allItems.FindNext();
}

UPDATE 1:

Additional research using OutlookSpy shows that the problem is not in our code - the Start\End dates are incorrect inside the API when Cached Exchange Mode is off. But Outlook developers were aware of it, and they somehow display correct dates in calendars! Does anyone know how?

UPDATE 2:

Answer from Outlook Support Escalation Engineer:

Based on this, I can confirm that this is a problem in our product.

1. What is your code? 2. Do not use WebDAV; it is deprecated. — Dmitry Streblechenko
Looks perfectly fine... What is your code that accesses the appointment? Do you ever access AppointmentItem.Parent (which will give you the master appointment for an instance of a recurring activity)? — Dmitry Streblechenko
I've updated the code above. No, we don't use AppointmentItem.Parent. Anyway, before we access Start and End dates, we access only Subject, ResponseStatus and MeetingStatus properties of AppointmentItem. — Bolick
For one thing, Outlook does not use OOM to display the Calendar folder contents, secondly, why do you think the Start/End dates are incorrect? What exactly is wrong? — Dmitry Streblechenko
Exactly: OutlookSpy shows us several appointments with the same StartTime, in our case = 11/01/2012, and this is definitly the master appointment of recurring weekly activity (the same organizer, the same subject, etc). But in calendar we can see correct picture - one item in each week. I would very appreciate if You could explain how Outlook works, what technology does it use to display calendar, any ideas why we get wrong result in OOM and how to fix these errors? — Bolick

Jose Manuel Gomez Alvarez Jose Manuel Gomez Alvarez · Accepted Answer · 2018-05-28T08:28:50

Possible cause:

Sort after setting IncludeRecurrences.

Here is my code of a PowerShell module that retrieves Outlook items between two dates.

And a little applet to check for changes and send an email including the agenda updates, which comes handy when you don't have mobile access to the Exchange.

Path: Documents\WindowsPowerShell\Modules\Outlook\expcal.ps1

Function Get-OutlookCalendar
{
  <#
   .Synopsis
    This function returns appointment items from default Outlook profile
   .Description
    This function returns appointment items from the default Outlook profile. It uses the Outlook interop assembly to use the olFolderCalendar enumeration.
    It creates a custom object consisting of Subject, Start, Duration, Location
    for each appointment item.
   .Example
    Get-OutlookCalendar |
    where-object { $_.start -gt [datetime]"5/10/2011" -AND $_.start -lt `
    [datetime]"5/17/2011" } | sort-object Duration
    Displays subject, start, duration and location for all appointments that
    occur between 5/10/11 and 5/17/11 and sorts by duration of the appointment.
    The sort is the shortest appointment on top.
   .Notes
    NAME:  Get-OutlookCalendar
    AUTHOR: ed wilson, msft
    LASTEDIT: 05/10/2011 08:36:42
    KEYWORDS: Microsoft Outlook, Office
    HSG: HSG-05-24-2011
   .Link
     Http://www.ScriptingGuys.com/blog
 #Requires -Version 2.0
 #>

 echo Starting... Initialize variables

 Add-type -assembly "Microsoft.Office.Interop.Outlook" | out-null
 $olFolders = "Microsoft.Office.Interop.Outlook.OlDefaultFolders" -as [type]
 $olCalendarDetail = "Microsoft.Office.Interop.Outlook.OlCalendarDetail" -as [type]

 echo ... Getting ref to Outlook and Calendar ...

 $outlook = new-object -comobject outlook.application
 $namespace = $outlook.GetNameSpace("MAPI")
 $folder = $namespace.getDefaultFolder($olFolders::olFolderCalendar)

 echo ... Calculating dates ...

 $now = Get-Date -Hour 0 -Minute 00 -Second 00

 echo From $a To $b

 echo ... Getting appointments ...

 $Appointments = $folder.Items
 $Appointments.IncludeRecurrences = $true
 $Appointments.Sort("[Start]")

 echo ... Setting file names ...

 $oldfile = "$env:USERPROFILE\outlook-calendar.bak"
 echo oldfile: $oldfile
 $newfile = "$env:USERPROFILE\outlook-calendar.txt"
 echo newfile: $newfile
 $calfile = "$env:USERPROFILE\outlook-calendar.ics"
 echo calfile: $calfile

 echo ... Exporting calendar to $calfile ...

 $calendarSharing = $folder.GetCalendarExporter()
 $calendarSharing.CalendarDetail = $olCalendarDetail::olFullDetails
 $calendarSharing.IncludeWholeCalendar = $false
 $calendarSharing.IncludeAttachments = $false
 $calendarSharing.IncludePrivateDetails = $true
 $calendarSharing.RestrictToWorkingHours = $false
 $calendarSharing.StartDate = $now.AddDays(-30)
 $calendarSharing.EndDate = $now.AddDays(30)
 echo $calendarSharing
 $calendarSharing.SaveAsICal($calfile)

 echo ... Backing up $newfile into $oldfile ...

 if (!(Test-Path $newfile)) {
  echo "" |Out-File $newfile
 }

 # Backup old export into $oldfile
 if (Test-Path $oldfile) {
  echo "Deleting old backup file $oldfile"
  del $oldfile 
 }
 echo " ... moving $newfile into $oldfile ... "
 move $newfile $oldfile

 echo "... Generating text report to file $newfile ..."

 $Appointments | Where-object { $_.start -gt $now -AND $_.start -lt $now.AddDays(+7) } | 
  Select-Object -Property Subject, Start, Duration, Location, IsRecurring, RecurrenceState  |
  Sort-object Start |
  Out-File $newfile -Width 100

 echo "... Comparing with previous export for changes ..."

 $oldsize = (Get-Item $oldfile).length
 $newsize = (Get-Item $newfile).length

 if ($oldsize -ne $newsize ) {
  echo "!!! Detected calendar change. Sending email..."
  $mail = $outlook.CreateItem(0)

  #2 = high importance email header
  $mail.importance = 2

  $mail.subject = $env:computername + “ Outlook Calendar“

  $mail.Attachments.Add($newfile)
  $mail.Attachments.Add($calfile)
  $text = Get-Content $newfile | Out-String
  $mail.body = “See attached file...“ + $text

  #for multiple email, use semi-colon ; to separate
  $mail.To = “[email protected]“

  $mail.Send()

 }
 else {
  echo "No changes detected in Calendar!"
 }


} #end function Get-OutlookCalendar

Function Get-OutlookCalendarTest
{
 echo starting...
 Add-type -assembly "Microsoft.Office.Interop.Outlook" | out-null
 $olFolders = "Microsoft.Office.Interop.Outlook.OlDefaultFolders" -as [type]
 $outlook = new-object -comobject outlook.application
 $namespace = $outlook.GetNameSpace("MAPI")
 $folder = $namespace.getDefaultFolder($olFolders::olFolderCalendar)

 $a = Get-Date -Hour 0 -Minute 00 -Second 00
 $b = (Get-Date -Hour 0 -Minute 00 -Second 00).AddDays(7)
 echo From $a To $b

 $Appointments = $folder.Items
 $Appointments.IncludeRecurrences = $true
 $Appointments.Sort("[Start]")

 $Appointments | Where-object { $_.start -gt $a -AND $_.start -lt $b } | Select-Object -Property IsRecurring, RecurrenceState, Subject, Start, Location

} #end function Get-OutlookCalendarTest

This is the code to invoke the PowerShell function in the module:

Path: Documents\WindowsPowerShell\mono.ps1

Import-Module -Name Outlook\expcal.psm1 -Force

$i=0

#infinite loop for calling connect function   
while(1)
{
   $i = $i +1
   Write-Output "Running task Get-OutlookCalendar ($i)"
   Get-OutlookCalendar

   start-sleep -seconds 300

}

To run the PowerShell script, use powershell.exe. To run this on startup, a shortcut on "%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\":

C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -ExecutionPolicy Bypass "C:\Users\%USERNAME%\Documents\WindowsPowerShell\mono.ps1"

Retrieve calendar items (Outlook API, WebDAV) displaying strange behaviour

UPDATE 1:

UPDATE 2:

1 Answers