Complete test code for Lock-Object

Runspace2.ps1

$arrayList = New-Object System.Collections.ArrayList
$arrayList.AddRange(('a','b','c','d','e'))

$sessionstate = [System.Management.Automation.Runspaces.InitialSessionState]::CreateDefault()
$sessionstate.ImportPSModule("PSThreading")
$sessionstate.Variables.Add(
    (New-Object System.Management.Automation.Runspaces.SessionStateVariableEntry('arrayList', $arrayList, $null))
)

$runspacepool = [runspacefactory]::CreateRunspacePool(1, 2, $sessionstate, $Host)
$runspacepool.Open()

$ps1 = [powershell]::Create()
$ps1.RunspacePool = $runspacepool

# Note that the calls to Lock-Object in each PowerShell object are commented out here, to demonstrate what happens
# if you try to access objects concurrently without synchronization.  Uncomment them to have a successful test.

$null = $ps1.AddScript({
    #Lock-Object $arrayList.SyncRoot {
        for ($i = 1; $i -le 5; $i++)
        {
            Start-Sleep -Milliseconds 200
            $null = $arrayList.Add($i)
        }
    #}
})

$handle1 = $ps1.BeginInvoke()

$ps2 = [powershell]::Create()
$ps2.RunspacePool = $runspacepool

$null = $ps2.AddScript({
    #Lock-Object $arrayList.SyncRoot {
        foreach ($i in $arrayList)
        {
            Start-Sleep -Milliseconds 200
            $i
        }
    #}
})

$handle2 = $ps2.BeginInvoke()

if ([System.Threading.WaitHandle]::WaitAll($handle1.AsyncWaitHandle) -and
    [System.Threading.WaitHandle]::WaitAll($handle2.AsyncWaitHandle))
{
    $ps1.EndInvoke($handle1)
    $ps2.EndInvoke($handle2)
}

if ($ps1.HadErrors)
{
    foreach ($errorRecord in $ps1.Streams.Error)
    {
        Write-Error -ErrorRecord $errorRecord
    }
}

if ($ps2.HadErrors)
{
    foreach ($errorRecord in $ps2.Streams.Error)
    {
        Write-Error -ErrorRecord $errorRecord
    }
}