Powershell's adding Integers when populating arrayList

Question

I have a function in Powershell which populates a list with dictionaries.

Function Process-XML-Audit-File-To-Controls-List($nodelist){
    #Keep an array list to track the different controls
    $control_list = New-Object System.Collections.ArrayList
    foreach($var in $nodelist)
    {  
     $lines  = [string]($var.InnerText) -split '[\r\n]'
     $control_dict = @{}
     foreach($line in $lines){
         $line_split = $line.Trim() -split ':',2
         if($line_split.Length -eq 2){ 
             $control_dict.Add($line_split[0],$line_split[1])       
         }
     }
     $control_list.Add($control_dict)
    }
    return $control_list
}

Instead of receiving an ArrayList which returns only Hashtables it returns a list which has Int32 and Hashtable, where there is an Int32 in it for each hashtable element:

True     True     Int32                                    System.ValueType                                                                                  
True     True     Int32                                    System.ValueType                                                                                  
True     True     Int32                                    System.ValueType                                                                                                                                                                   
True     True     Hashtable                                System.Object                                                                                     
True     True     Hashtable                                System.Object                                                                                     
True     True     Hashtable                                System.Object

I'm not really sure why I have those integers in my ArrayList.

Mathias R. Jessen · Accepted Answer · 2015-07-13 10:44:27Z

11

The problem here is that ArrayList.Add() returns the index at which the new item was added. When you return $control_list, the integers representing the index locations have already been written to the pipeline

Prefix the method call with [void] to remove the output from Add():

[void]$control_list.Add($control_dict)

Or pipe to Out-Null:

$control_list.Add($control_dict) | Out-Null

answered Jul 13, 2015 at 10:44

Mathias R. Jessen

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Comments

Jaqueline Vanek · Accepted Answer · 2015-07-14 10:52:44Z

1

Why don't you just declare an empty array and then use "+=" instead of Add()?

$control_list = @()
$hash = [PSCustomObject]@{}
$control_list += $hash

Also, why do you parse the nodes as text?

answered Jul 14, 2015 at 10:52

Jaqueline Vanek

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Vesper · Accepted Answer · 2015-07-13 10:18:47Z

0

System.Collections.ArrayList::Add() adds objects, not pairs of key-value, so when you do this $control_dict.Add($line_split[0],$line_split[1]) you are adding two objects, one integer and one hashtable. If you want to use integers as keys instead, you should use a hashtable property assignment, like this:

$control_dict.($line_split[0]) = $line_split[1]

You need to wrap the $line_split[0] into brackets so that the proper key would be added, otherwise the value queried will be $control_dict.$line_split which is valid as hash tables accept objects as keys, and null as never assigned, and then getting [0] out of null value will net you an exception.

answered Jul 13, 2015 at 10:18

Vesper

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1 Comment

Lucas Kauffman Over a year ago

Except $control_dict is of type hashtable no? Just tried your method and it still yields the same

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