Objects with no '.Count' Property - use of @() (array subexpression operator) vs. [Array] cast

user_8303961 0
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I am trying to perform some simple if statements, but all of the newer cmdlets that are based upon [Microsoft.Management.Infrastructure.CimInstance] don't seem to expose a .count method?

$Disks = Get-Disk
$Disks.Count

Doesn't return anything. I found that I can cast this as an [array], which makes it returns a .NET .count method as expected.

[Array]$Disks = Get-Disk
$Disks.Count

This works without directly casting it as an array for previous cmdlets:

(Get-Services).Count

What is the recommended way to get around this?

An example that doesn't work:

$PageDisk = Get-Disk | Where {($_.IsBoot -eq $False) -and ($_.IsSystem -eq $False)}
  If ($PageDisk.Count -lt 1) {Write-Host "No suitable drives."; Continue}
   Else If ($PageDisk.Count -gt 1) {Write-Host "Too many drives found, manually select it."}
   Else If ($PageDisk.Count -eq 1) { Do X }

Option A (Cast as Array):

[Array]$PageDisk = Get-Disk | Where {($_.IsBoot -eq $False) -and ($_.IsSystem -eq $False)}
  If ($PageDisk.Count -lt 1) {Write-Host "No suitable drives."; Continue}
   Else If ($PageDisk.Count -gt 1) {Write-Host "Too many drives found, manually select it."}
   Else If ($PageDisk.Count -eq 1) { Do X }

Option B (Use Array Indexes):

 $PageDisk = Get-Disk | Where {($_.IsBoot -eq $False) -and ($_.IsSystem -eq $False)}
  If ($PageDisk[0] -eq $Null) {Write-Host "No suitable drives."; Continue}
   Else If ($PageDisk[1] -ne $Null) {Write-Host "Too many drives found, manually select it."}
   Else If (($PageDisk[0] -ne $Null) -and (PageDisk[1] -eq $Null)) { Do X }

Option C (Array) -Thanks to @PetSerAl :

$PageDisk = @(Get-Disk | Where {($_.IsBoot -eq $False) -and ($_.IsSystem -eq $False)})
  If ($PageDisk.Count -lt 1) {Write-Host "No suitable drives."; Continue}
   Else If ($PageDisk.Count -gt 1) {Write-Host "Too many drives found, manually select it."}
   Else If ($PageDisk.Count -eq 1) { Do X }

What is the reason for CIM based cmdlets not exposing the .Count method? What is the recommended way to handle this? Option B seems convoluted to me, and hard to read. Option A works, but shouldn't powershell cast this as an array for me? Am I going about this in entirely the wrong way?

cim scalar powershell-cmdlet powershell arrays
2 Answers

@mklement0 has a great answer, but one thing to add: if your script (or the script calling yours) has Set-StrictMode, the automatic .Count and .Length properties stop working:

$ Set-StrictMode -off
$ (42).Length
1
$ Set-StrictMode -Version Latest
$ (42).Length
ParentContainsErrorRecordException: The property 'Length' cannot be found on this object. Verify that the property exists.

To be safe, you can wrap any unknown variable in an array @(...) before checking the length:

$ $result = Get-Something
$ @($result).Length
1
user_7717680
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