Remove powershell object from objects array

Question

I have a huge pscustomobject Array1, and a second smaller Array2 containing text/strings. I want to remove objects from Array1 which have specific status in Array2. For example, remove from Array1 all elements with Array2.object.status = "Removed".

I don't want to create another Objects array using -contains or -notcontains. I know how to do it but I am looking for something more sophisticated, I was trying to convert my arrays to --> [System.Collections.ArrayList], like here --> $Array = [System.Collections.ArrayList]$Array. I tried to use "Remove" and "RemoveAt" methods but still getting the same error

Error:

 Exception calling "Remove" with "1" argument(s): "Collection was of a fixed size.

Below please find extract from my code:

$Array1 = [System.Collections.ArrayList]$Array1 
$Array1 = obj1, obj2, obj3 #contains pscustomobjects, with multiple 
properties
$Array2 = text1, text2, text3 #contains status names, only strings/text

foreach ($element in $Array1) {
if ($Array2 -contains $element.status) {
$Array1.Remove($element)
}
}

iRon · Accepted Answer · 2019-09-06 15:00:29Z

1

This is actually not the philosophy behind PowerShell which is best in using pipelines (see: understanding pipelines especially when using huge PSCustomObject arrays. Meaning that you should leave the array intact and filter the concerned objects on the fly with the Where-Object, like:

$Array1 | Where-Object {$Array2 -Contains $_.status} | ...

edited Sep 6, 2019 at 15:00

answered Sep 6, 2019 at 14:53

iRon

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5 Comments

tester81 Over a year ago

Its not about the Pipelins, pls read my description, I was asking about removing objects from the objects array.

iRon Over a year ago

Yes, I have read that, for several reasons, I am just recommending you to use the pipelines for huge files.

ninMonkey Over a year ago

For the non-pipeline version you can remove items from an array using $array = 'a', 'b', 'c'; $array -ne 'b' which removes b -- when using comparison operators and the LHS is not scalar, it filters the list by the test

iRon Over a year ago

@ninMonkey, yes, that is the semantic PowerShell way to do this. Note that it is similar to -contains or -notcontains except that it does a literal (not)match. Besides, it also uses the pipeline for output which is by fact PowerShell's nature but often dismissed (and under estimated) by C# programmers as "not sophisticated". Arrays are mutual, which means you have to translate into e.g. a ArrayList where you create an extra step and lose performance and the easy PowerShell syntax (unless you can combine this with another part of the solution).

iRon Over a year ago

See also: the performance of a complete (PowerShell) solution is supposed to be better than the sum of its parts

Jeff Zeitlin · Accepted Answer · 2019-09-06 11:48:08Z

0

It is likely that your problem is that $Array1 is no longer a [System.Collections.ArrayList]; you're assigning to it with = and a comma list of objects. Instead, try using

$Array1 = [System.Collections.ArrayList]$Array1 
# Not this...
# $Array1 = obj1, obj2, obj3 #contains pscustomobjects, with multiple properties

# This, instead...
(obj1, obj2, obj3) | ForEach-Object { $Array1.Add($_) }

$Array2 = text1, text2, text3 #contains status names, only strings/text

foreach ($element in $Array1) {
if ($Array2 -contains $element.status) {
$Array1.Remove($element)
}
}

You might also be able to do

[System.Collections.ArrayList]$Array1 = obj1, obj2, obj3
# Not this...
# $Array1 = obj1, obj2, obj3 #contains pscustomobjects, with multiple properties

$Array2 = text1, text2, text3 #contains status names, only strings/text

foreach ($element in $Array1) {
if ($Array2 -contains $element.status) {
$Array1.Remove($element)
}
}

answered Sep 6, 2019 at 11:48

Jeff Zeitlin

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3 Comments

ninMonkey Over a year ago

The official docs say you should replace ArrayList with a List for better performance (and other reasons) learn.microsoft.com/en-us/dotnet/api/…

Jeff Zeitlin Over a year ago

@ninMonkey - I've not found any way to use parameterized classes (e.g., List<T>) in PowerShell.

ninMonkey Over a year ago

it's [list[t]] --- using namespace System.Collections.Generic; $numbers = [list[int]]::new() $numbers.Add(40)

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