Problem with PSCustomObject data collection - azure

Question

I'm preparing a table with information about VM name and provision date of OS disk. I can easily retrieve that information from $VM.disks.statuses.time[0] command, if individual VM is assigned to $VM, but I when i try to collect data into table, I got an error:
Cannot index into a null array.
At line:4 char:1
+ [PSCustomObject]#{
+ ~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : NullArray
This is my code:
$VMs = Get-AzVM -status
$vmOutput = $VMs | ForEach-Object {
[PSCustomObject]#{
"VM Name" = $_.Name
"Provision Date" = $_.disks.statuses.time[0].ToString()
}
}

Answer 1

I can reproduce your issue, the issue was caused by the outputs of Get-AzVM -status and Get-AzVM -ResourceGroupName <ResourceGroupName> -Name <Name> -Status are different.
The output of Get-AzVM -status will not has the disks property, but when you get individual VM status via Get-AzVM -ResourceGroupName <ResourceGroupName> -Name <Name> -Status, it will have the property, so you got the error.
Get-AzVM -status:
Get-AzVM -ResourceGroupName <ResourceGroupName> -Name <Name> -Status:
Solution:
To fix the issue, just to use Get-AzVM -ResourceGroupName <ResourceGroupName> -Name <Name> -Status in your script.
$VMs = Get-AzVM -status
$vmOutput = $VMs | ForEach-Object {
$VMstatus = Get-AzVM -ResourceGroupName $_.ResourceGroupName -Name $_.Name -Status
[PSCustomObject]#{
"VM Name" = $VMstatus.Name
"Provision Date" = $VMstatus.disks.statuses.time[0].ToString()
}
}

Answer 2

You can use the Get-AzDisk command to retrieve disk creation information.
$disks = Get-AzDisk | Where-Object { $_.Managedby }
$vmOutput = foreach ($disk in $disks) {
[pscustomobject]#{"VM Name" = ($disk.ManagedBy -split "/")[-1]
"Provisioned Date" = $disk.TimeCreated
}
}

Answer 3

The error says:
Cannot index into a null array.
So my guess is that something here $_.disks.statuses.time[0].ToString() is $null. Therefore you should add some $nullchecks:
$VMs = Get-AzVM -status
$vmOutput = $VMs | ForEach-Object {
if ($_.disks -and $_.disks.statuses -and $_.disks.statuses.time -and ($_.disks.statuses.time.Count -gt 0)){
[PSCustomObject]#{
"VM Name" = $_.Name
"Provision Date" = $_.disks.statuses.time[0].ToString()
}
}
}
Hope that helps.