Custom powershell cmdlets do not support multi-threading?

Question

In the code blocks below, I'm trying to run Get-MyCmdlet in 3 separate threads, each of which opens a google page if the Get-MyCmdlet did not give anything.

The Get-MyCmdlet is fairly simple, the only thing it does is WriteObject("hello world"); (defined in the c# code).

However the script always opens up a google page, unless I change the Get-MyCmdlet to Get-Host(which is a system default cmdlet).

Is it because the custom cmdlets are not supporting multi-threading? Any help will be greatly appreciated!

The cmdlet:

[Cmdlet(VerbsCommon.Get, "MyCmdlet ")]
public class GetMyCmdlet  : Cmdlet
{
    protected override void ProcessRecord()
    {
         WriteObject("hello world");
    }
}

the script:

$ScriptBlock = { 

        $result = Get-MyCmdlet 

        if (!$result) {[System.Diagnostics.Process]::Start("http://www.google.com")}

        $name = ($result | get-member)[-1].name
        $result = $result.$name
        return $result
}

....

$threads = 3
    for ($i = 0; $i -lt $threads) {

        $running = @($jobs | Where-Object {$_.State -match 'Running'})

        Write-Host $running.length
        if ($running.length -lt $threads) {

            $jobs += Start-job -ScriptBlock $ScriptBlock


            $i = $i + 1

        } else {
            get-job | receive-job
            $finished = @($jobs | Where-Object ($_.State -match 'Completed'))  

            if ($finished) {
                $finished.getType()
                foreach($job in $finished) {
                    Receive-Job -keep $job | Out-File "Output$.txt"
                    $i = $i + 1
                    $finished.Remove($job)
                    Remove-Job -job $job
                }
            }  
        }   
    }

Answer 1

No custom cmdlets are not the problem. My guess is the problem is that calling Get-MyCmdlet fails with an error so $result is not set and thanks to your if the browser is started. If you would check the results of your jobs you would see an error message. You probably need to make sure the job initializes right so you can call your cmdlet. You could use the -InitializationScript parameter of Start-Job to import your module for the job. See here, here and here for more information.