Test-Connection $False will not convert to ArrayList - arrays

Question

Currently working on making a new report that will be generated with PowerShell. Using PowerShell to build a HTML email. I have one other report working fine but ran into an unexpected issue on this one.
The below code is just s sample from the script I am still building. Still adding pieces to the script but testing it as I move forward. I added a Test-Connection to see if a computer was responding or not and lost the ability to build an array.
My final goal with this report is to import a list of names from a file and then loop over all of the computers to see if they are pinging and gather some information from them using Get-WMIObject, etc.
The below code will replicate the issue I am having but I am not sure how to solve it. I've narrowed down the issue to when Test-Connection returns 'False'. On line 26 I am filtering for just results that returned a 'False' on Test-Connection to save them into its own array so that I can use that array in a different part of my code to build the HTML table/HTML to send out the email.
Only the flipside, if I tell it to look for only 'True', it will save into the array without issue.
This is the error that PowerShell is giving when doing filtering by 'False'.
Cannot convert value "#{Computer_Name=Computer1; Ping_Status=False}" to type "System.Collections.ArrayList". Error: "Cannot convert the "#{Computer_Name=Computer1 Ping_Status=False}" value of type "Selected.System.Management.Automation.PSCustomObject" to type "System.Collections.ArrayList"."
Please let me know if there is any other information that I can provide. I've been stuck on this one for a while. Co-workers are even say this is a weird one.
Is there something unique about the way Test-Connection return a 'False'?
CLS
[string]$ErrorActionPreference = "Continue"
[System.Collections.ArrayList]$Names = #(
"Computer1"
"Computer2"
)
[System.Collections.ArrayList]$WMI_Array = #()
[System.Collections.ArrayList]$Ping_Status_False = #()
foreach ($Name in $Names) {
[bool]$Ping_Status = Test-Connection $Name -Count 1 -Quiet
$WMI_Array_Object = [PSCustomObject]#{
'Computer_Name' = $Name
'Ping_Status' = $Ping_Status
}
$WMI_Array.Add($WMI_Array_Object) | Out-Null
}
$WMI_Array | Format-Table
[System.Collections.ArrayList]$Ping_Status_False = $WMI_Array | Where-Object {$_.Ping_Status -eq $false} | Select-Object Computer_Name, Ping_Status
$Ping_Status_False

Answer 1

The problem is not Test-Connection but that this statement
$WMI_Array | Where-Object {$_.Ping_Status -eq $false} | Select-Object Computer_Name, Ping_Status
produces just a single result. Which is not an array, and can thus not be converted to an ArrayList. The behavior is identical when you filter for $_.PingStatus -eq $true with just a single matching object, so I suspect that you had either more than one successfully pinged host or none at all when you tested that condition and it didn't throw the same error.
You could mitigate the problem by wrapping the statement in the array subexpression operator:
[Collections.ArrayList]$Ping_Status_False = #($WMI_Array |
Where-Object {$_.Ping_Status -eq $false} |
Select-Object Computer_Name, Ping_Status)
Or, you could simply drop all the pointless type-casting from your code:
$ErrorActionPreference = "Continue"
$Names = 'Computer1', 'Computer2'
$WMI_Array = foreach ($Name in $Names) {
[PSCustomObject]#{
'Computer_Name' = $Name
'Ping_Status' = [bool](Test-Connection $Name -Count 1 -Quiet)
}
}
$WMI_Array | Where-Object { -not $_.Ping_Status }