Add elements to arry in powershell - powershell

Question

I want to simply add some numbers to an array and then sort them via powershell, however, the following code seems to be wrong
$myArray = New-Object System.Collections.ArrayList
Foreach ($Name in $VMName) {
$Tokens = $Name.Split(".")
$myArray.Add($Tokens[$Tokens.Count-1])
}
Write-Host($myArray | Sort-Object)
The error is
+ $myArray.Add($Tokens[$Tokens.Count-1])
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : NotSupportedException
How can I fix that?
The variable $Name is something like 101.u18.uab.14 or 103.win10.template or 102.win7.pink.18 and so on. Each $Name has some . symbols and I want to tokenize them and get the last element for each of them. So, in this example, I want to see a sorted 14 18 template.
UPDATE:
The provided methods seems to be incorrect.
1- This method by Steven
$myArray = New-Object System.Collections.ArrayList
Foreach ($Name in $VMName) {
$Tokens = $Name.Split(".")
[Void]$myArray.Add($Tokens[-1])
}
shows this error
Exception calling "Add" with "1" argument(s): "Collection was of a fixed size."
At C:\Users\user\Desktop\get_ip_list.ps1:20 char:5
+ [Void]$myArray.Add($Tokens[-1])
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : NotSupportedException
2- This method by Santiago
$myArray = [Collections.Generic.List[string]]::new()
Foreach ($Name in $VMName) {
[Void]$myArray.Add($Name.Split(".")[-1])
}
Shows the following error
Exception calling "Add" with "1" argument(s): "Collection was of a fixed size."
At C:\Users\user\Desktop\get_ip_list.ps1:19 char:5
+ [Void]$myArray.Add($Name.Split(".")[-1])
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : NotSupportedException
If I have missed your point in the above codes, please let me know.

Answer 1

I think you are missing the first line from the error. However it looks like you are simply trying to add the last elements from the $Tokens array. In that case you don't need to reference the index like that, below should work:
$myArray = New-Object System.Collections.ArrayList
Foreach ($Name in $VMName) {
$Tokens = $Name.Split(".")
[Void]$myArray.Add($Tokens[-1])
}
Notice the addition of [Void] this will stop the .Add() method from returning the index number it just added to.
Also note you can create array list objects using casting like:
$myArray = [Collections.ArrayList]#()
Update to Address Continued Errors:
The only thing I can think of to cause the error "Collection was of a fixed size." is if you've previously type constrained the variable.
Example:
[String[]]$myArray = #()
# Posibly a whole bunch of other things happening maybe in the console or IDE.
$myArray = [Collections.ArrayList]#()
$myArray.Add('something')
Results:
Exception calling "Add" with "1" argument(s): "Collection was of a fixed size."
At line:1 char:1
+ $myArray.Add('something')...
In this case they type of the $myArray will not change to [Collections.ArrayList]. The problem will be transparent up until you try to use the .Add() method that won't work. This is because an array list is easily and therefore silently cast back to a [String[]] or [Object[]].
Note: If you were to run $myArray.IsFixedSize it would return "True".
My guess as to what's happening; at some point while developing your code or perhaps in the larger script, $myArray got type constrained, and stuck in the scope. This can definitely happen especially given the scope overlap in IDE's like PowerShell's ISE, and I think it happens in VSCode as well. If this is part of a larger script look for instances of $myArray to see if it's indeed type constrained and make corrections as needed. Otherwise a simply restarting your session might do the trick.

Answer 2

Honestly, not sure how could you be getting that error unless the array we're looping through is actually something different. Steven's answer should work fine, I'll put this code below just to show that the results we get are the ones you expect:
$col = [Collections.Generic.List[String]]::new()
$vmName = #(
'101.u18.uab.14'
'103.win10.template'
'102.win7.pink.18'
)
ForEach($name in $vmName)
{
$col.Add($name.Split('.')[-1])
}

Answer 3

if you want absolutly use array you can simply do it :
$Array=#()
$VMName | %{
$Value=($_.Split('.'))[-1]
$Array+= $Value
}
$Array| sort
Otherwise you can simply do it :
$VMName | %{($_.Split('.'))[-1]} | sort