[image] david-zemdegs:
Initialise my output array.
Most of the times thats unnecessary.
[image] david-zemdegs:
on each loop initialise an internal array and populate it.
Why does it have to be a newly initialized array in each iteration?
[image] david-zemdegs:
At the end of each … Answer from Olaf on forums.powershell.org
PowerShell Test-Path
powershellfaqs.com › convert-an-arraylist-to-an-array-in-powershell
How to Convert an ArrayList to an Array in PowerShell?
February 9, 2024 - The most straightforward way to convert an ArrayList to an array in PowerShell is by using the ToArray() method. This method is a member of the ArrayList class and converts the entire ArrayList into an array.
Adam the Automator
adamtheautomator.com › powershell-array
PowerShell Arrays, ArrayLists & Collections: Best Practices
Below you can see that you need to explicitly create an ArrayList object using the New-Object cmdlet or by casting a standard array to an ArrayList object. Notice that in this case the BaseType is an object whereas the above examples have BaseTypes of Arrays which exhibit inheritance from the Object class. Ultimately, PowerShell is providing access to the .NET type system.
Published April 22, 2025
Adding arrays to arraylists
I have an object which is of type {system.collections.arraylist] To add a single element I can use the Add method but to add an array I have to use the ‘+=’ method. Does anyone have a technical explanation for this as ‘+=’ doesnt seem to be in the microsoft doco below: I am also assuming ... More on forums.powershell.org
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0
July 11, 2022Powershell converts ArrayList to Array - Stack Overflow
@wOxxOm Thanks for the suggestion, the reason I am using ArrayList is that I need to remove the elements in it dynamically. Maybe I should try LinkedList but if it still returns Array, I have to find a workaround. More on stackoverflow.com
Convert system.collection arrylist to string array
A couple of ways to do this. In particular, it depends on whether you really want an array of strings or just one big string. Let's set up the example: $list = [System.Collections.ArrayList]::new() [void]$list.AddRange(('x','y','z')) For an array of strings, use the ToArray() method: $list.ToArray() You can also pass in the type of the array you want if you want the array to be [string[]] rather than [object[]]: $list.ToArray([string]) But you can also just join the elements of the ArrayList together to get one big string: $list -join "`r`n" More on reddit.com
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September 1, 2020How to create an ArrayList from an Array in PowerShell? - Stack Overflow
I've got a list of files in an array. I want to enumerate those files, and remove specific files from it. Obviously I can't remove items from an array, so I want to use an ArrayList. But the follow... More on stackoverflow.com
Videos
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PowerShell 7 Tutorial 8: Interacting with Arrays, ArrayLists, ...
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PowerShell 7 Tutorial 7: Introduction to Array and ArrayList - YouTube
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PowerShell 7 Tutorials for Beginners #3 : Array & ArrayList - YouTube
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PowerShell Array and ArrayList - storing multiple items as a one ...
SharePoint Diary
sharepointdiary.com › sharepoint diary › powershell › powershell tutorials › powershell arraylist – a beginners guide!
PowerShell ArrayList - A Beginners Guide! - SharePoint Diary
September 30, 2025 - In this comprehensive guide, we will delve into the depths of the PowerShell ArrayList, from creation to manipulation, uncovering its features and benefits, troubleshooting common errors, and sharing tips to optimize your script performance. Understanding ArrayList and Its Benefits in PowerShell ... PowerShell ArrayList vs. Array: Key differences
PowerShell Forums
forums.powershell.org › powershell help
Adding arrays to arraylists - PowerShell Help - PowerShell Forums
July 11, 2022 - I have an object which is of type {system.collections.arraylist] To add a single element I can use the Add method but to add an array I have to use the ‘+=’ method. Does anyone have a technical explanation for this as ‘+=’ doesnt seem to be in the microsoft doco below: I am also assuming ...
Stack Overflow
stackoverflow.com › questions › 40475813 › powershell-converts-arraylist-to-array
Powershell converts ArrayList to Array - Stack Overflow
December 20, 2016 - Convert the normal array produced via foreach expression to arraylist in the end: [Collections.ArrayList]$entryList and it'll be still faster!
Java2Blog
java2blog.com › home › powershell › powershell array › convert array to arraylist in powershell
Convert Array to ArrayList in PowerShell [2 Ways] - Java2Blog
April 16, 2023 - Cast array object to System.Collections.ArrayList to convert array to ArrayList in PowerShell.
Enterprise DNA
blog.enterprisedna.co › powershell-arraylist
Powershell ArrayList: How to Build Better Scripts – Master Data Skills + AI
In this section, we will cover ... ... This will create a new empty array with an initial size of 10. To add items to an ArrayList, you can use the Add() method....
Reddit
reddit.com › r/powershell › convert system.collection arrylist to string array
r/PowerShell on Reddit: Convert system.collection arrylist to string array
September 1, 2020 -
I am new to Powershell and this is an enhancement to the first script I have written. I have the following Copy item just an example of 1. The script will have about 5 total pointing to different servers Copy-Item -Path \xxx\prod\y.txt -Destination \zzz\test\ -Force -PassThru -ErrorAction "SilentlyContinue" -ErrorVariable +ProcessError -Verbose What I want to do is convert the System.Collections.ArryList ProcessError to a string array that I can include in the body of an email. How do I do this?
Top answer 1 of 4
4
A couple of ways to do this. In particular, it depends on whether you really want an array of strings or just one big string. Let's set up the example: $list = [System.Collections.ArrayList]::new() [void]$list.AddRange(('x','y','z')) For an array of strings, use the ToArray() method: $list.ToArray() You can also pass in the type of the array you want if you want the array to be [string[]] rather than [object[]]: $list.ToArray([string]) But you can also just join the elements of the ArrayList together to get one big string: $list -join "`r`n"
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From your note about sending this via email I'm guessing that you only want the exception messages an not the whole error record. You can get this from a property called Exception, then use -join to add new lines between each record: $ErrorsBody = $ProcessError.Exception -join "`n" $body = @" The following errors occured: $ErrorsBody "@ If you are sending html messages you might prefer it as a table: $ErrorsBody = $ProcessError | Select Exception,TargetObject,FullyQualifedErrorId | ConvertTo-HTML -fragment
Top answer 1 of 2
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I can't get that constructor to work either. This however seems to work:
# $temp = Get-ResourceFiles
$resourceFiles = New-Object System.Collections.ArrayList($null)
$resourceFiles.AddRange($temp)
You can also pass an integer in the constructor to set an initial capacity.
What do you mean when you say you want to enumerate the files? Why can't you just filter the wanted values into a fresh array?
Edit:
It seems that you can use the array constructor like this:
$resourceFiles = New-Object System.Collections.ArrayList(,$someArray)
Note the comma. I believe what is happening is that when you call a .NET method, you always pass parameters as an array. PowerShell unpacks that array and passes it to the method as separate parameters. In this case, we don't want PowerShell to unpack the array; we want to pass the array as a single unit. Now, the comma operator creates arrays. So PowerShell unpacks the array, then we create the array again with the comma operator. I think that is what is going on.
2 of 2
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Probably the shortest version:
[System.Collections.ArrayList]$someArray
It is also faster because it does not call relatively expensive New-Object.
SPGuides
spguides.com › powershell-arraylist
PowerShell ArrayList [Create and Use]
March 26, 2025 - In this tutorial, I will explain how to create and use PowerShell ArrayList with some examples for efficient data management. As a PowerShell developer or administrator when you start using ArrayList over an Array, it will improve your script’s performance.
IDERA
idera.com › home › using efficient lists in powershell
Using Efficient Lists in PowerShell | IDERA
April 22, 2025 - That’s because “+=” is really a lie, and PowerShell actually needs to create a new larger array and copy the contents from the old to the new array. This works well with just a few additions but causes exponential delays once you need to add more than just a few new elements. The most common workaround is using the System.Collections.ArrayList ...
Wit IT
witit.blog › array-vs-arraylist-powershell
Array vs ArrayList (PowerShell) - Wit IT - witit
December 22, 2022 - First, let’s look at an easy way to define it: [Collections.ArrayList]$ArrayList = @('thing1','thing2') Secondly, let’s check the type with the GetType() method: Sweet! It’s an ArrayList! But why does it matter? Well, let’s check if it’s fixed size or not. Well give me an ice cream cone and call me Joe Biden! An array list isn’t fixed.
Microsoft Learn
learn.microsoft.com › en-us › dotnet › api › system.collections.arraylist.toarray
ArrayList.ToArray Method (System.Collections) | Microsoft Learn
The elements are copied using Array.Copy, which is an O(n) operation, where n is Count. ... Copies the elements of the ArrayList to a new array of the specified element type.
Microsoft Learn
learn.microsoft.com › en-us › powershell › scripting › learn › deep-dives › everything-about-arrays
Everything you wanted to know about arrays - PowerShell | Microsoft Learn
Adding items to an array is one of its biggest limitations, but there are a few other collections that we can turn to that solve this problem. The ArrayList is commonly one of the first things that we think of when we need an array that is faster to work with.
LazyAdmin
lazyadmin.nl › home › how to use powershell array – complete guide
How to Use PowerShell Array - Complete Guide — LazyAdmin
January 19, 2023 - Retrieving items from the ArrayList is the same as with a normal array. You can use the index or loop through all the items in the array using one of the loop methods. There are a couple of built-in cmdlets that can be used to perform common array operations. These cmdlets make it easier to work with arrays and allow you to automate tasks. Some of the most commonly used built-in array cmdlets in PowerShell are:
Varonis
varonis.com › blog › powershell-array
PowerShell Array Guide: How to Use and Create
June 9, 2022 - Here, we can use the default .Net constructor to create a new ArrayList, and then using the -Add operator to add items to it. The [void] operator is there because sometimes these commands throw out strange outputs that can mess with the code. These are the most common array types in PowerShell, but ...
| How
pipe.how › new-arraylist
PowerShell Collections: ArrayList | How
January 17, 2020 - From the side indicators we can see that Array implemements the same interfaces as ArrayList, but has a few more as well. This is because Array is a generic class that needs to be typed, as we did during the last post when creating specifically typed arrays, or what PowerShell does for us when creating an Object[]. The `1 is the .NET representation of how many type parameters there are on the given generic type, its so-called arity.
Microsoft Certified Professional Magazine
mcpmag.com › articles › 2019 › 04 › 10 › managing-arrays-in-powershell.aspx
Managing Arrays in PowerShell -- Microsoft Certified Professional Magazine Online
How to read, add and modify array elements -- with a few curve balls along the way. ... In PowerShell and many languages, an array is a set of items all represented by a single variable. To explain arrays and how to manage them in PowerShell, let's start with the example of a set of colors.
Netwrix
blog.netwrix.com › home › resources › how to use powershell arrays
How to Use PowerShell Arrays | Netwrix
December 13, 2024 - The size of an array in PowerShell is immutable once it is defined. However, the operator += enables you to create a new array by appending items to an existing array — essentially creating a new combined array.
Reddit
reddit.com › r/powershell › when to use array vs array list vs list
r/PowerShell on Reddit: When to use array vs array list vs list
April 25, 2022 - Array: When you don't need to dynamically add items to a collection outside a loop. ArrayList: Never. Generic list: When you do need to dynamically add items to a collection outside a loop. Arrays are the default output type in PowerShell. Whenever you run an expression that outputs multiple items you will get a System.Object array.