Exception calling "Add" with "2" argument(s): "Key cannot be null.

When you updated it to remove the CSV, did you bring across the addition of the distinguishedName (from Get-Mailbox)? It only throws that error based on the content of $DataB, and only if the indexed field (distinguishedName) is null.

The only changes I made were removing the top 2 lines:

$DataA = Import-CSV D:\Import\DataA.csv
$DataB = Import-CSV D:\Import\DataB.csv

And changing the variable before Get-ADUser to $DataA and for Get-MailboxStatistics to $DataB. The strange thing is that when I request the $DataA and $DataB variables separately, I do not see the distinguishedname column. I tried to use Clear-Varable $DataA and $DataB but without success. It appears as if something is wrong with these variables, because the exports that I make do contain the DN columns.

It's not that you've reverted to the previous version where distinguishedName wasn't populating is it?

Can you share the snippets you're adding again?

No, I have not reverted to the previous version. The DistinguishedName is included in both commands. I'm using the following script:

$DataA = Get-ADUser -SearchBase "OU=Users,DC=Contoso,DC=com" -SearchScope 1 -Properties samaccountname,LastLogon,whenCreated,distinguishedname 
-Filter {LastLogon -lt $time -AND enabled -eq $true -AND whenCreated -lt $time} | 
          select-object SamAccountName,Name,@{Name="LastLogon"; Expression={[DateTime]::FromFileTime($_.lastLogon).ToString('yyyy-MM-dd hh:mm:ss')}},
          WhenCreated,@{Name="ReferenceDate"; Expression={($datetoday)}},
          @{N='ADAccountDaysInactive'; E={$($(Get-Date) - $([DateTime]::FromFileTime($_.lastLogon))).Days}},distinguishedname | 
          Export-CSV -Path D:\Export\DataA.csv -NoTypeInformation -Append -Encoding UTF8

$mbxall = Get-Mailbox -ResultSize Unlimited -OrganizationalUnit $dnou | Where {$_.OrganizationalUnit -eq "Contoso.com/Users"} |
        Select-Object alias,displayname,distinguishedname
		$mbxinactive = ForEach($mbx in $mbxall)
		{
		  $DataB = Get-MailboxStatistics $mbx.alias | where {$_.LastLogonTime -lt $time -AND $_.WhenMailboxCreated -lt $time} | 
          Select-Object displayname,lastlogontime,lastloggedonuseraccount,@{Name="ReferenceDate"; Expression={($datetoday)}},
          @{N='MailboxDaysInactive'; E={ ((Get-Date) - ($_.LastLogonTime)).Days} },@{N='DistinguishedName'; E={($mbx.distinguishedname)} } |
          Export-CSV -Path D:\Export\DataB.csv -NoTypeInformation -Append
        }

$properties = $DataA[0].PSObject.Properties.Name + $DataB[0].PSObject.Properties.Name

$IndexedProperty = 'distinguishedName'

$DataBIndex = @{}
for ($i = 0; $i -lt $DataB.Count; $i++) {
    $DataBIndex.Add($DataB[$i].$IndexedProperty, $i)
}

foreach ($itemA in $DataA) {
    if ($DataBIndex.Contains($itemA.$IndexedProperty)) {
        $itemB = $DataB[$DataBIndex.($itemA.$IndexedProperty)]

        foreach ($property in $itemB.PSObject.Properties) {
            $itemA | Add-Member $property.Name $property.Value
        }
 
        $itemA | Select-Object $properties | Export-CSV D:\Export\Result.csv -Append -NoTypeInformation
    }
}

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Normally, I would import the exports that are made here into $DataA and $DataB and then it would work.

You still have export-csv for DataB (so no output to assign).

And the scope for DataB means it would never hold information for more than one mailbox.

I'm on a train, I'll post a more detailed fix when I'm home if you haven't fixed it yourself.

Thank you Chris that looks much better. Unfortunately I'm not able to test this right now. I'll be able to test this tomorrow morning & then I'll also answer the questions.

Good morning Chris,

When I run the new script, I run into the following error. I can verify that the old script still works, and all Exchange and Active Directory commands are available in the shell (working from ISE connecting to our Exchange 2010 server). I tried looking for a solution, suggesting to use ForEach instead of ForEach-Object, but without success. When I run Get-PSSession I can verify that my current Exchange session is in the state of "Opened".

ERROR: System.Management.Automation.PSInvalidOperationException: No valid sessions were specified.  Ensure you provide valid sessions that are in the Opened state and are available to run commands.
   at Microsoft.PowerShell.Commands.InvokeCommandCommand.BeginProcessing()
   at System.Management.Automation.Cmdlet.DoBeginProcessing()
   at System.Management.Automation.CommandProcessorBase.DoBegin()

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As for your questions:
1. To be honest I have not heard of LastLogonDate, but only for LastLogon and LastLogonTimeStamp. If I understand correctly, the LastLogon gets the time stamp from the domain controller on which the query is run, whereas LastLogonTimeStamp is replicated to all domain controllers in the domain, but is inaccurate to a maximum of 14 days(?). In our situation, we have only 2 domain controllers, so it may be better to include a simple ForEach cycle to query each domain controller and get the highest logon time stamp from LastLogon. But maybe the LastLogonDate is better, I don't know. The purpose of the script is to identify enabled users that have not logged on to their AD account AND Exchange mailbox for at least 60 days.

2 & 3. TotalDays, how is this better than the current situation? The only thing we calculate is the number of days since the LastLogon time, and based on that value, decide wether a user is inactive or not (if the Exchange inactive days also equals or exceeds 60 days of inactivity) and then disable those users. When this works correctly, I would be expanding the script to identity disabled users (from another OU) and find users that exceed 180 days of inactivity (for deletion).

This is currently the entire script:

Import-Module ActiveDirectory
$exuri = ‘http://exchangeserver.contoso.com/PowerShell/?SerializationLevel=Full’
$ExSession = New-PSSession –ConfigurationName Microsoft.Exchange –ConnectionUri $exuri -Credential $Credentials –Authentication Kerberos
Import-PSSession $ExSession

$DaysInactive = 60
$time = (Get-Date).Adddays(-($DaysInactive))
$datetoday = (Get-Date).ToString('yyyy-MM-dd hh:mm:ss')
$dnou = "OU=Users,DC=Contoso,DC=com"
$ErrorActionPreference = 'SilentlyContinue'
   
$dataAParams = @{
    SearchBase  = "OU=User,DC=Contoso,DC=com"
    SearchScope = 'OneLevel'
    Properties  = 'samaccountname', 'LastLogon', 'whenCreated', 'distinguishedname'
    Filter      = { LastLogon -lt $time -AND enabled -eq $true -AND whenCreated -lt $time }
}
$DataA = Get-ADUser @dataAParams |
    Select-Object SamAccountName,
                  Name,
                  @{Name="LastLogon"; Expression={ [DateTime]::FromFileTime($_.lastLogon).ToString('yyyy-MM-dd hh:mm:ss') }},
                  WhenCreated,
                  @{Name="ReferenceDate"; Expression={ $datetoday }},
                  @{Name='ADAccountDaysInactive'; Expression={ ((Get-Date) - ([DateTime]::FromFileTime($_.lastLogon))).Days }},
                  distinguishedname

$DataB = Get-Mailbox -ResultSize Unlimited -OrganizationalUnit $dnou | 
    Where { $_.OrganizationalUnit -eq "Contoso.com/Users" } |
    ForEach-Object {
        $mailbox = $_

        $_ | Get-MailboxStatistics | Where {$_.LastLogonTime -lt $time -AND $_.WhenMailboxCreated -lt $time} |
            Select-Object DisplayName,
                          LastLogonTime,
                          LastLoggedOnUserAccount,
                          @{Name="ReferenceDate"; Expression={ $datetoday }},
                          @{Name='MailboxDaysInactive'; Expression={ ((Get-Date) - ($_.LastLogonTime)).Days }},
                          @{Name='DistinguishedName'; Expression={ $mailbox.distinguishedname }}
    }

$properties = $DataA[0].PSObject.Properties.Name + $DataB[0].PSObject.Properties.Name

$IndexedProperty = 'distinguishedName'

$DataBIndex = @{}
for ($i = 0; $i -lt $DataB.Count; $i++) {
    $DataBIndex.Add($DataB[$i].$IndexedProperty, $i)
}

foreach ($itemA in $DataA) {
    if ($DataBIndex.Contains($itemA.$IndexedProperty)) {
        $itemB = $DataB[$DataBIndex.($itemA.$IndexedProperty)]

        foreach ($property in $itemB.PSObject.Properties) {
            $itemA | Add-Member $property.Name $property.Value
        }
 
        $itemA | Select-Object $properties | Export-CSV D:\Export\Result.csv -Append -NoTypeInformation
    }
}

Remove-PSSession $ExSession

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When I try this approach I get the following error:

ERROR: System.Management.Automation.RuntimeException: Cannot index into a null array.
   at System.Management.Automation.ExceptionHandlingOps.CheckActionPreference(FunctionContext funcContext, Exception exception)
   at System.Management.Automation.Interpreter.ActionCallInstruction`2.Run(InterpretedFrame frame)
   at System.Management.Automation.Interpreter.EnterTryCatchFinallyInstruction.Run(InterpretedFrame frame)
   at System.Management.Automation.Interpreter.EnterTryCatchFinallyInstruction.Run(InterpretedFrame frame)

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Not liking me much, is it?

Does $DataB have values this time?

Haha indeed! Just checked and $DataB is empty right now. $DataA does have values including the DN.

Please can we run this modified version to verify you're getting something (anything) back:

$mailboxes = Get-Mailbox -ResultSize Unlimited -OrganizationalUnit $dnou | 
    Where { $_.OrganizationalUnit -eq "Contoso.com/Users" }
foreach ($mailbox in $mailboxes) {
    Get-MailboxStatistics -Identity $mailbox.Identity | Where {$_.LastLogonTime -lt $time -AND $_.WhenMailboxCreated -lt $time} |
        Select-Object DisplayName,
                      LastLogonTime,
                      LastLoggedOnUserAccount,
                      @{Name="ReferenceDate"; Expression={ $datetoday }},
                      @{Name='MailboxDaysInactive'; Expression={ ((Get-Date) - ($_.LastLogonTime)).Days }},
                      @{Name='DistinguishedName'; Expression={ $mailbox.distinguishedname }}
}

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Certainly, I can verify that I do get an output then including the DN.

Still getting the "No valid sessions were specified.  Ensure you provide valid sessions that are in the Opened state and are available to run commands.". The $DataA is populated, $DataB is not. The script:

$DaysInactive = 60
$time = (Get-Date).Adddays(-($DaysInactive))
$datetoday = (Get-Date).ToString('yyyy-MM-dd hh:mm:ss')
$dnou = "OU"
$ErrorActionPreference = 'SilentlyContinue'

$dataAParams = @{
    SearchBase  = "OU"
    SearchScope = 'OneLevel'
    Properties  = 'samaccountname', 'LastLogon', 'whenCreated', 'distinguishedname'
    Filter      = { LastLogon -lt $time -AND enabled -eq $true -AND whenCreated -lt $time }
}
$DataA = Get-ADUser @dataAParams |
    Select-Object SamAccountName,
                  Name,
                  @{Name="LastLogon"; Expression={ [DateTime]::FromFileTime($_.lastLogon).ToString('yyyy-MM-dd hh:mm:ss') }},
                  WhenCreated,
                  @{Name="ReferenceDate"; Expression={ $datetoday }},
                  @{Name='ADAccountDaysInactive'; Expression={ ((Get-Date) - ([DateTime]::FromFileTime($_.lastLogon))).Days }},
                  distinguishedname

$mailboxes = Get-Mailbox -ResultSize Unlimited -OrganizationalUnit $dnou | 
    Where { $_.OrganizationalUnit -eq "OU" }
$DataB = New-Object System.Collections.Generic.List[PSObject]
foreach ($mailbox in $mailboxes) {
    $result = Get-MailboxStatistics -Identity $mailbox.Identity | Where {$_.LastLogonTime -lt $time -AND $_.WhenMailboxCreated -lt $time} |
        Select-Object DisplayName,
                      LastLogonTime,
                      LastLoggedOnUserAccount,
                      @{Name="ReferenceDate"; Expression={ $datetoday }},
                      @{Name='MailboxDaysInactive'; Expression={ ((Get-Date) - ($_.LastLogonTime)).Days }},
                      @{Name='DistinguishedName'; Expression={ $mailbox.distinguishedname }}
    $DataB.Add($result)
}
$DataB = $DataB.ToArray()

$properties = $DataA[0].PSObject.Properties.Name + $DataB[0].PSObject.Properties.Name

$IndexedProperty = 'distinguishedName'

$DataBIndex = @{}
for ($i = 0; $i -lt $DataB.Count; $i++) {
    $DataBIndex.Add($DataB[$i].$IndexedProperty, $i)
}

foreach ($itemA in $DataA) {
    if ($DataBIndex.Contains($itemA.$IndexedProperty)) {
        $itemB = $DataB[$DataBIndex.($itemA.$IndexedProperty)]

        foreach ($property in $itemB.PSObject.Properties) {
            $itemA | Add-Member $property.Name $property.Value
        }
 
        $itemA | Select-Object $properties | Export-CSV D:\Export\Result.csv -Append -NoTypeInformation
    }
}

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Both versions work. The first one exports the CSV with output and the second one, if I request $DataB it is populated.

Cool, let's forget the modified versions and go with the one that works then. Anything more starts to become a waste of time for you.

Hi Chris,

Thank you. The script works now! Additionally, I've tried to implement the ForEach cycle for the DC's, but I'm not sure if I did it correctly. Hope you can check it.

$DaysInactive = 60
$Time = (Get-Date).Adddays(-($DaysInactive))
$CurrentTimeStamp = (Get-Date).ToString('yyyy-MM-dd hh:mm:ss')
$OrganizationalUnit = "OU=Users,DC=nl,DC=Contoso,DC=com"
$OrganizationalUnit2 = "Contoso.com/Users"
$DomainControllers = Get-ADDomainController -Filter {Name -like "*"}
$ErrorActionPreference = 'SilentlyContinue'

$dataAParams = @{
    SearchBase  = "OU=Users,DC=Contoso,DC=com"
    SearchScope = 'OneLevel'
    Properties  = 'samaccountname', 'LastLogon', 'whenCreated', 'distinguishedname'
    Filter      = { LastLogon -lt $Time -AND enabled -eq $true -AND whenCreated -lt $Time }
    Server      = $DomainControllerHostname
}
foreach($DomainController in $DomainControllers)
{
$DomainControllerHostname = $DomainController.HostName
$DataA = Get-ADUser @dataAParams |
    Select-Object SamAccountName,
                  Name,
                  @{Name="LastLogon"; Expression={ [DateTime]::FromFileTime($_.lastLogon).ToString('yyyy-MM-dd hh:mm:ss') }},
                  WhenCreated,
                  @{Name="ReferenceDate"; Expression={ $CurrentTimeStamp }},
                  @{Name='ADAccountDaysInactive'; Expression={ ((Get-Date) - ([DateTime]::FromFileTime($_.lastLogon))).Days }},
                  distinguishedname
}

$AllMailboxes = Get-Mailbox -ResultSize Unlimited -OrganizationalUnit $OrganizationalUnit | 
    Where {$_.OrganizationalUnit -eq $OrganizationalUnit2} |
    Select-Object alias,displayname,distinguishedname

$DataB = @()
$InactiveMailbox = ForEach($Mailbox in $AllMailboxes) {
    $DataB += Get-MailboxStatistics $Mailbox.alias | Where {$_.LastLogonTime -lt $Time -AND $_.WhenMailboxCreated -lt $Time} | 
        Select-Object displayname,
                      lastlogontime,
                      lastloggedonuseraccount,
                      @{Name="ReferenceDate"; Expression={($CurrentTimeStamp)}},
                      @{Name='MailboxDaysInactive'; Expression={ ((Get-Date) - ($_.LastLogonTime)).Days} },
                      @{Name='DistinguishedName'; Expression={($Mailbox.distinguishedname)} }
}

$properties = $DataA[0].PSObject.Properties.Name + $DataB[0].PSObject.Properties.Name

$IndexedProperty = 'distinguishedName'
$DataBIndex = @{}
for ($i = 0; $i -lt $DataB.Count; $i++) {
    $DataBIndex.Add($DataB[$i].$IndexedProperty, $i)
}

foreach ($itemA in $DataA) {
    if ($DataBIndex.Contains($itemA.$IndexedProperty)) {
        $itemB = $DataB[$DataBIndex.($itemA.$IndexedProperty)]

        foreach ($property in $itemB.PSObject.Properties) {
            $itemA | Add-Member $property.Name $property.Value
        }
 
        $itemA | Select-Object $properties | Export-CSV -Path D:\Export\Result.csv -Append -NoTypeInformation
    }
}

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Thank you Chris. The script still works now, I do get a very similar output as yesterday, only difference now is that it appears that the data/columns with LastLogon etc. is missing in the export. When I open the export I see all the information of the mailboxes, but not the AD users. The first 3 columns are now "IsSynchronized", "SyncRoot" and "Count". When I request $DataA, the information is there.

$DaysInactive = 60
$Time = (Get-Date).Adddays(-($DaysInactive))
$CurrentTimeStamp = (Get-Date).ToString('yyyy-MM-dd hh:mm:ss')
$OrganizationalUnit = "OU=Users,DC=Contoso,DC=com"
$OrganizationalUnit_Format = "Contoso.com/Users"
$DomainControllers = Get-ADDomainController -Filter {Name -like "*"}
$ErrorActionPreference = 'SilentlyContinue'

$DataAValues = @{}
foreach($DomainController in $DomainControllers) {
    $DomainControllerHostname = $DomainController.HostName
    $dataAParams = @{
        SearchBase  = "OU=Users,DC=Contoso,DC=com"
        SearchScope = 'OneLevel'
        Properties  = 'samaccountname', 'LastLogon', 'whenCreated', 'distinguishedname'
        Filter      = { LastLogon -lt $Time -AND enabled -eq $true -AND whenCreated -lt $Time }
        Server      = $DomainControllerHostname
    }
    Get-ADUser @dataAParams |
        Select-Object SamAccountName,
                    Name,
                    @{Name="LastLogon"; Expression={ [DateTime]::FromFileTime($_.lastLogon).ToString('yyyy-MM-dd hh:mm:ss') }},
                    WhenCreated,
                    @{Name="ReferenceDate"; Expression={ $CurrentTimeStamp }},
                    @{Name='ADAccountDaysInactive'; Expression={ ((Get-Date) - ([DateTime]::FromFileTime($_.lastLogon))).Days }},
                    distinguishedname |
        ForEach-Object {
            if ($DataAValues.Contains($_.SamAccountName)) {
                if ($DataAValues[$_.SamAccountName].LastLogon -lt $_.LastLogon) {
                    $DataAValues[$_.SamAccountName].LastLogon = $_.LastLogon
                }
            } else {
                $DataAValues.Add($_.SamAccountName, $_)
            }
        }
}
$DataA = $DataAValues.Values

$AllMailboxes = Get-Mailbox -ResultSize Unlimited -OrganizationalUnit $OrganizationalUnit | 
    Where {$_.OrganizationalUnit -eq $OrganizationalUnit_Format} |
    Select-Object alias,displayname,distinguishedname

$DataB = @()
$InactiveMailbox = ForEach($Mailbox in $AllMailboxes) {
    $DataB += Get-MailboxStatistics $Mailbox.alias | Where {$_.LastLogonTime -lt $Time -AND $_.WhenMailboxCreated -lt $Time} | 
        Select-Object displayname,
                      lastlogontime,
                      lastloggedonuseraccount,
                      @{Name="ReferenceDate"; Expression={($CurrentTimeStamp)}},
                      @{Name='MailboxDaysInactive'; Expression={ ((Get-Date) - ($_.LastLogonTime)).Days} },
                      @{Name='DistinguishedName'; Expression={($Mailbox.distinguishedname)} }
}

$properties = $DataA[0].PSObject.Properties.Name + $DataB[0].PSObject.Properties.Name

$IndexedProperty = 'distinguishedName'
$DataBIndex = @{}
for ($i = 0; $i -lt $DataB.Count; $i++) {
    $DataBIndex.Add($DataB[$i].$IndexedProperty, $i)
}

foreach ($itemA in $DataA) {
    if ($DataBIndex.Contains($itemA.$IndexedProperty)) {
        $itemB = $DataB[$DataBIndex.($itemA.$IndexedProperty)]

        foreach ($property in $itemB.PSObject.Properties) {
            $itemA | Add-Member $property.Name $property.Value
        }
 
        $itemA | Select-Object $properties | Export-CSV -Path D:\Export\Result.csv -Append -NoTypeInformation
    }
}

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Thanks very much Chris it all works now! Have a great day.