UseUsingScopeModifierInNewRunspaces.md

UseUsingScopeModifierInNewRunspaces

Severity Level: Warning

Description

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

• Invoke-Command *
• Workflow { InlineScript {}}
• Foreach-Object **
• Start-Job
• Start-ThreadJob
• The Script resource in DSC configurations, specifically for the GetScript, TestScript and SetScript properties

* Only with the -ComputerName or -Session parameter.
** Only with the -Parallel parameter

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 }