Arrays

PowerShell: Passing an ArrayList of Objects into another Script as an Argument

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I am trying to pass an ArrayList that contains objects into another PowerShell script to execute something further.

The error message that I am receiving is:

“Cannot process argument transformation on parameter ‘al’. Cannot convert the “System.Collections.Hashable System.Collections.Hashable System.Collections.Hashable” value of type “System.String” to type “System.Collections.ArrayList””

In script1.ps1:

$al = New-Object System.Collections.ArrayList

...

$obj =  @{"var1"="apple"; "var2"="banana"; "var3"="carrot";}
$al.Add($obj)

...


foreach ($i in $al) {
    $temp = $($i.var1)
    write-host "$temp"     #outputs "apple" correctly
}

invoke-expression -Command "script2.ps1 -al '$al'"

In script2.ps1:

param ([System.Collections.ArrayList]$al)

...

foreach ($i in $al) {
    $temp = $($i.var1)
    write-host "$temp"     #error message
}

Answer

For a reason that I’m not familiar with, Invoke-Expression is converting your ArrayList to a HashTable. If you really need an ArrayList in script2.ps1, you can make $al a global variable (see below).

Updated script1.ps1

$al = New-Object System.Collections.ArrayList
$obj = @{"var1" = "apple"; "var2" = "banana"; "var3" = "carrot"; }
$al.Add($obj)

foreach ($i in $al) {
    $temp = $($i.var1)
    write-host "$temp"     
}

$Global:al = $al

invoke-expression -Command "$PSScriptRootscript2.ps1"

Updated script2.ps1

param()

$Global:al.GetType().FullName

foreach ($i in $Global:al) {
    $temp = $($i.var1)
    write-host "$temp"     
}