Add new set of values to ArrayList

Question

So I have the following ArrayList stored in $var:

ip_prefix   region         string   
0.0.0.0/24  GLOBAL         Something
0.0.0.0/24  GLOBAL         Something
0.0.0.0/24  GLOBAL         Something
0.0.0.0/24  GLOBAL         Something

I need to add a row to this however the following code returns an error:

$var.add("127.0.0.1/32", "GLOBAL", "something")

Error:

Cannot find an overload for "Add" and the argument count: "3".
At line:1 char:1
+ $awsips.add("127.0.0.1/32", "GLOBAL", "SOMETHING")
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodException
    + FullyQualifiedErrorId : MethodCountCouldNotFindBest

I'm sure it's something simple I have to adjust, however Google searches had me going around in circles.

Hi there. Have a look here. stackoverflow.com/questions/11266013/…. Looks like you are adding to an array of objects. So you would need to set the properties of the new object when adding — SQLAndOtherStuffGuy
– SQLAndOtherStuffGuy, Commented Aug 2, 2017 at 11:20

David Brabant · Accepted Answer · 2017-08-02 11:27:11Z

4

$var = New-Object System.Collections.ArrayList
$var.Add(@{"ip_prefix" = "0.0.0.0/24"; "region" = "GLOBAL"; string = "Something"})
$var.Add(@{"ip_prefix" = "127.0.0.1/32"; "region" = "GLOBAL"; string = "SOMETHING"})

$var
$var | %{ Write-Output "$($_.ip_prefix), $($_.region), $($_.string)" }

Or:

$var = @()
$var += @{"ip_prefix" = "0.0.0.0/24"; "region" = "GLOBAL"; string = "Something"}
$var += @{"ip_prefix" = "127.0.0.1/32"; "region" = "GLOBAL"; string = "SOMETHING"}

answered Aug 2, 2017 at 11:27

David Brabant

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1 Comment

Ansgar Wiechers Over a year ago

@{...} -> [PSCustomObject]@{...}

SQLAndOtherStuffGuy · Accepted Answer · 2017-08-02 12:09:33Z

3

Should do the job

   $obj = New-Object PSObject -Property @{            
        ip_prefix = "0.0.0.0/24"                
        region = "GLOBAL"              
        string = "Something"           
    }    

$var+= $obj

edited Aug 2, 2017 at 12:09

answered Aug 2, 2017 at 11:23

SQLAndOtherStuffGuy

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2 Comments

Ansgar Wiechers Over a year ago

This is the correct approach, but I'd use PSObject rather than Object, and pass the list of properties as a hashtable to New-Object rather than adding each property individually. On PowerShell v3 and newer the method of choice is using the [PSCustomObject] type accelerator directly on the property hashtable.

SQLAndOtherStuffGuy Over a year ago

Good advice. I've amended the code to reflect this.

Ansgar Wiechers · Accepted Answer · 2017-08-03 21:12:32Z

Your output suggests that your array list contains custom objects with properties ip_prefix, region, and string.

You therefore need to add a single object with the desired property values to your array list.

By contrast, you attempted to add 3 indvividual elements to the array list, which is not only conceptually wrong, but also fails syntactically, given that the .Add() method only accepts a single argument (technically, there is a method for adding multiple items, .AddRange()).

In PSv3+, syntax [pscustomobject]@{...} constructs a custom object from a hashtable literal with the definition order of the entries preserved.

$null = $var.Add(
  [pscustomobject] @{ ip_prefix="127.0.0.1/32"; region="GLOBAL"; string="something" }
)

Note how $null = ... is used to suppress the .Add() method's output (the index at which the item was inserted).

SQLAndOtherStuffGuy's answer is on the right track, but beware that $var += ... silently replaces the array list stored in $var with a regular PowerShell array ([System.Object[]]).

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