Edit

UseUsingScopeModifierInNewRunspaces

  • Article

Severity Level: Warning

Description

If a scriptblock is intended to be run in a new runspace, variables inside it should use the $using: scope modifier, or be initialized within the scriptblock. This applies to:

  • Invoke-Command- Only with the ComputerName or Session parameter.
  • Workflow { InlineScript {} }
  • Foreach-Object - Only with the Parallel parameter
  • Start-Job
  • Start-ThreadJob
  • The Script resource in DSC configurations, specifically for the GetScript, TestScript and SetScript properties.

How to Fix

Within the ScriptBlock, instead of just using a variable from the parent scope, you have to add the using: scope modifier to it.

Example

Wrong

$var = 'foo'
1..2 | ForEach-Object -Parallel { $var }

Correct

$var = 'foo'
1..2 | ForEach-Object -Parallel { $using:var }

More correct examples

$bar = 'bar'
Invoke-Command -ComputerName 'foo' -ScriptBlock { $using:bar }

$bar = 'bar'
$s = New-PSSession -ComputerName 'foo'
Invoke-Command -Session $s -ScriptBlock { $using:bar }

# Remark: Workflow is supported on Windows PowerShell only
Workflow {
    $foo = 'foo'
    InlineScript { $using:foo }
}

$foo = 'foo'
Start-ThreadJob -ScriptBlock { $using:foo }
Start-Job -ScriptBlock {$using:foo }