I have some script write on PowerShell and I have some problem. When I run this script I have some error in output:

You cannot call a method on a null-valued expression.
At C:\scripts\exchange_rep_work_cp.ps1:133 char:82
+ $mbx | add-member -membertype noteproperty -value $stats.TotalItemSize.Value.ToMB <<<< () -name TotalSize
+ CategoryInfo : InvalidOperation: (ToMB:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull

You cannot call a method on a null-valued expression.

This error repeat few times. This is the line of code (133):

130 $tmp = ""
131 $Mailboxes | foreach {
132 #Name_of_company has a diffrent domain and domain controller
133 if ($Company -eq "Name_of_company"){
134 $stats = get-mailboxstatistics -DomainController zzzz.xxx.yyyyyy.local -id $_ | where >135 {$.ObjectClass –eq “Mailbox”} }
136 else {
137 $stats = get-mailboxstatistics -id $
| where {$.ObjectClass –eq “Mailbox”}}
138 $MBx = new-object system.object
139 $tmp = $
.EmailAddresses | foreach { if ($_ -notmatch "yyyyyy.local") { $.AddressString } }
140: $Country = $
141: $Types = $_.Customattribute2
142: $mbx | add-member -membertype noteproperty -value $stats.Displayname -name DisplayName
143: $mbx | add-member -membertype noteproperty -value $stats.TotalItemSize.Value.ToMB() -name TotalSize

Please give me some advise what's wrong


2 Answers 2


It says you are trying to call the ToMB method on a string called $stats.TotalItemSize.Value. This is a [string] and it does not have that method.


Do you run the script on a computer with the Exchange Management Shell installed? This also includes some datatypes Exchange uses to represent sizes, and without those such errors are quite common. A valid test would be to check if the error is present when running it on an Exchange server.

Also your code for connecting to the Exchange remoting instance would be interesting to see.

EDIT: Your code is missing some underscores here and there, so the stats object will in some cases never be filled. Here's a short explanation:

$a = "" | select Name, Value
$a.Name = "Trond"
$a.value = "Yes"

$array = @()
$array += $a

$array | where {$.Name -eq "Trond"}

$array | where {$_.Name -eq "Trond"}

So, in short: This line:

$stats = get-mailboxstatistics -id $ | where {$.ObjectClass –eq “Mailbox”}}

Will never produce a "$stats" object, which I'm suspecting is why your code fails. If you're using the PowerShell 3.0 ISE you shold be able to see that the ISE doesn't "understand" your filtering and shows that by not coloring the dollar sign red.

  • Yes this script is run on the server with the Exchange Management Shell, and on this server there is Exchange.
    – spy86
    Sep 24, 2013 at 14:21
  • Could you post more of the script? We need to see whats inside the $stats variable.
    – Trondh
    Sep 25, 2013 at 11:14
  • Yes sure , please take look on code
    – spy86
    Sep 27, 2013 at 7:05

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