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UseUsingScopeModifierInNewRunspaces.md

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description ms.custom ms.date ms.topic title
Use 'Using:' scope modifier in RunSpace ScriptBlocks
PSSA v1.21.0
10/18/2021
reference
UseUsingScopeModifierInNewRunspaces

UseUsingScopeModifierInNewRunspaces

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 }