Friday, August 11, 2017

Generic Folder Picker for Mailboxes for use in REST based Powershell Office365 / MSExchange Scripts

This is a continuance of my Office365/Exchange 2016 Rest series, in this post I'll be showing how some of the new GUI elements in the Exch-Rest module can help improve the speed and usability of any scripts where you need to browse Mailbox folders. What this modification to the Module does is allows you to enumerate all the Mail Folders in a Mailbox using the REST API and then present a simple folder tree that then allows you to browse through the folder in a Mailbox you might be looking for and when you double click that folder it will then return that as an object that can be piped into further operations. eg the new cmdlet works like

Invoke-MailFolderPicker -MailboxName -AccessToken $AccessToken

and visually this is what it looks like

I have one extra feature I've added into the module that allows you to return the same folder tree as above with the folder sizes in MB. To do this you need to make sure of the Extended Property (PR_MESSAGE_SIZE_EXTENDED Mapi property). To use this run the Invoke-MailFolderPicker cmdlet with the -ShowFolderSize switch eg

Invoke-MailFolderPicker -MailboxName -AccessToken $AccessToken -ShowFolderSize 

will return something like

How it works 

The Invoke-MailFolderPicker cmdlet is an amalgam of other functions in the Exch-Rest module (this is actually the main reason I've been building this module in the first place while the individual functions within the module are relatively easy to reproduce you need a large library of these small functions to build things that are really interesting and useful). 

So to build a Tree we first need a root so getting the Root Folder of the Mailbox is done using

$rootFolder = Get-RootMailFolder -AccessToken $AccessToken -MailboxName $MailboxName

The important part here is to know the Id of the root folder so when you look at the parent FolderId properties of any child folder you can construct a Tree of folders from that.

To cater for Foldersizes if the ShowFolderSize switch  is used you need to use an Extended property because there is no strongly typed property for FolderSize that is returned by the REST API (this was the same in EWS as well). To do this the following code snippet is used

    $PropList = @()
    $FolderSizeProp = Get-TaggedProperty -Id "0x0E08" -DataType Long
    $PropList += $FolderSizeProp
    $Folders = Get-AllMailFolders -MailboxName $MailboxName -AccessToken $AccessToken -PropList $PropList

This builds out the correct expansion string for these extended properties as well as catering for the differences between the graph and Outlook endpoints. The Get-AllMailFolder cmdlets just gets all the child folders of the Mailbox and returns them as a collection. Finally the 

 Invoke-FolderPicker -MailboxName $MailboxName -Folders $Folders -rootFolder $rootFolder -pickerType mail -ShowFolderSize

Using the Windows form and the Treeview control to build a visual representation of the Mailbox folder tree and return it to initiator.

Practical use

I've come up with a practical sample of this located that will once you double click the target folder will return the last 10 items in a folder to the PowerShell window. This is a simple 4 line script including the code to get the Token

$MailboxName = ""
$AccessToken = Get-AccessToken -MailboxName $MailboxName -ClientId 5471030d-f311-4c5d-91ef-74ca885463a7 -redirectUrl urn:ietf:wg:oauth:2.0:oob -ResourceURL
$FolderSelected = Invoke-MailFolderPicker -MailboxName $MailboxName -AccessToken $AccessToken -ShowFolderSize
Get-FolderItems -AccessToken $AccessToken -MailboxName $MailboxName -Folder $FolderSelected -Top 10 -TopOnly:$true -ReturnSize | Select Subject,
All the scripts in this blog require version 2.1 of the Exch-Rest module from the PowerShell gallery