Powershell Object properties get overwritten when new objects added to an array

Question

Here is my code:

$problems = New-Object System.Collections.ArrayList

$problemObj = New-Object psobject -Property @{
    problemName        = "abc"
    problemDescription = $null
}

$problemObj.problemDescription = "def"
$problems.Add($problemObj)

$problemObj.problemDescription = "ghi"
$problems.Add($problemObj)

$problems

And here is the output:

problemName problemDescription
----------- ------------------
abc         ghi
abc         ghi

I don't get what's wrong and why the first member gets modified. Any idea?

Thanks,

Does this answer your question? [How to create new clone instance of PSObject object](https://stackoverflow.com/questions/9581568/how-to-create-new-clone-instance-of-psobject-object) — OwlsSleeping, Jan 11 '22 at 10:35
Just to add a bit of detail on the duplicate flag- your problem is that PsObject copies by reference rather than value. — OwlsSleeping, Jan 11 '22 at 10:36

score 1 · Answer 1 · answered Jan 11 '22 at 10:43

You're not creating new objects - you're modifying and re-adding the same object to the list multiple times.

A common pattern for solving this is to re-use a dictionary as a template, then cast to [pscustomobject] to create new objects based on it:

$problems = New-Object System.Collections.ArrayList

# Create ordered dictionary to function as object template
$problemTemplate = [ordered]@{
    problemName        = "abc"
    problemDescription = $null
}

# modify template
$problemTemplate.problemDescription = "def"

# create new object, add to list
$problemObj = [pscustomobject]$problemTemplate
$problems.Add($problemObj)

# modify template again
$problemTemplate.problemDescription = "ghi"

# create another object, add to list
$problemObj = [pscustomobject]$problemTemplate
$problems.Add($problemObj)

$problems

Powershell Object properties get overwritten when new objects added to an array

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