Validate Expression Success with if condition in powershell

I am attempting to run a long PowerCLI command in a powershell script and output to the console based on its success. The command is executing and succeeding but NOT triggering the success output.

I tried making the entire command a variable but with no success. I suspect there is a more advanced way to do this that I am just not aware of.

Try{      
        #get list of all vms
        Write-Host "Collecting data and adding to file..."
        [Environment]::NewLine
        #create list of VMs in a variable
        $vmList = Get-VM -ErrorAction Stop


        #collect the VMWare Disk List here.
        #run the list through the appropriate filters and prompt for success (failure will initiate the catch)
        if ($vmList | Where-Object {$_.PowerState -eq "PoweredOff" -and $_.ExtensionData.config.ManagedBy.ExtensionKey -ne 'com.vmware.vcDr'} | Select-Object Name, @{N="Disk (GB)"; E={[math]::Round(($_ | Get-HardDisk | Measure-Object CapacityGB -Sum).sum)}}, @{N="Power State"; E={$_.PowerState}} | Export-Csv -Append -LiteralPath c:\temp\VMdiskTotals.csv) {
        Write-Host "vCenter Disk Collection for " $vcenter " Successful!"
        }

        }
Catch{
            Write-Host "Failed to collect the data from " $vcenter.Vcenter -ForegroundColor Red
            }

I want this to run the command, and if it completes with no error to output:

"vCenter Disk Collection for " $vcenter " Successful!"

if the command produces ANY error, it should trigger the catch and output:

Write-Host "Failed to collect the data from " $vcenter.Vcenter -ForegroundColor Red

Solution

It's still not clear why you need to put everything in an if statement. But perhaps this would work for you:

try {
    $vmList = Get-Vm -ErrorAction Stop
    if ($vmList) {  # If there are any VM objects in the array
        "vCenter Disk Collection for $vcenter Successful!"
        $vmList | Where-Object {$_.PowerState -eq "PoweredOff" -and $_.ExtensionData.config.ManagedBy.ExtensionKey -ne 'com.vmware.vcDr'} | 
            Select-Object Name, @{N="Disk (GB)"; E={[math]::Round(($_ | Get-HardDisk | Measure-Object CapacityGB -Sum).sum)}}, @{N="Power State"; E={$_.PowerState}} | 
            Export-Csv -Path c:\temp\VMdiskTotals.csv -Append -ErrorAction Stop
        "Successfully outputted to file."
    }
    else {
        "No VMs found."
    }
}
catch [VMware.VimAutomation.Sdk.Types.V1.ErrorHandling.VimException.VimException] {
    "Search for VMs failed."
}
catch [System.IO.IOException] {
    "Unable to write to file."
}
catch {
    "Other catch."
    $Error[0]
}