Listbox in powershell - Collection or Multidimensional Array?

Updated: In the example below I am going to use computers from Active Directory using Import-Module ActiveDirectory

In order to add items to your listbox with a multidimensional array, we can utilize an Object and the NoteProperty to add to the listbox

Ex:

#This example I am grabbing all computers from AD with the OS of windows server -- all windows servers
Import-Module ActiveDirectory
#Using the Name property for reboot and the Description for the listbox... you can use a different attribute if you like
$Computers = Get-ADComputer -filter {OperatingSystem -like "Windows Server*" -and Enabled -eq $true} -Properties Name, Description, OperatingSystem  | Select Name, Description, OperatingSystem

$listboxCollection =@()

foreach($Computer in $Computers)
{

    $Object = New-Object Object 
    $Object | Add-Member -type NoteProperty -Name CompName -Value $Computer.Name
    $Object | Add-Member -type NoteProperty -Name Values -Value $Computer.Description
    #fill the $listboxCollection
    $listboxCollection += $Object
}

#Add collection to the $listbox
$listBox.Items.AddRange($listboxCollection)

If you were to display your form from here, all your entries would show as System.Object. To get the Decription from each collection in the $listboxCollection to show we have tell it the ValueMember and DisplayMember.

Ex:

#This is using the properties above to display the correct item
$listBox.ValueMember = "CompName"
$listBox.DisplayMember = "Values"

Keeping with your original post, to get the selected item of the listbox on the OK button, you will need to put in a condition. However, there are several different ways to handle this event.

Ex:

#show form as dialog
$result = $form.ShowDialog()

if($result = [System.Windows.Forms.DialogResult]::OK)
{
    $selectedComputer = $listBox.SelectedItem.CompName  
    Restart-Computer -ComputerName $selectedComputer -Credential Get-Credential Domain\Username -Force
}

The variable $selectedComputer will be the selected computer. Note: In this example there is nothing checking to make sure there is a valid selection.

Complete Solution:

Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing


#This example I am grabbing all computers from AD with the OS of windows server -- all windows servers
Import-Module ActiveDirectory
#Using the Name property for reboot and the Description for the listbox... you can use a different attribute if you like
$Computers = Get-ADComputer -filter {OperatingSystem -like "Windows Server*" -and Enabled -eq $true} -Properties Name, Description, OperatingSystem  | Select Name, Description, OperatingSystem

$form = New-Object System.Windows.Forms.Form
$form.Text = 'Select a Computer'
$form.Size = New-Object System.Drawing.Size(300,200)
$form.StartPosition = 'CenterScreen'

$listBox = New-Object System.Windows.Forms.ListBox
$listBox.Location = New-Object System.Drawing.Point(10,40)
$listBox.Size = New-Object System.Drawing.Size(260,20)
$listBox.Height = 80

#create an empty collection to use later
$listboxCollection =@()

foreach($Computer in $Computers)
{

    $Object = New-Object Object 
    $Object | Add-Member -type NoteProperty -Name CompName -Value $Computer.Name
    $Object | Add-Member -type NoteProperty -Name Values -Value $Computer.Description
    $listboxCollection += $Object
}

$listBox.Items.AddRange($listboxCollection)

#This is using the properties above to display the correct item
$listBox.ValueMember = "CompName"
$listBox.DisplayMember = "Values"


#add listbox to form
$form.Controls.Add($listBox)

#Ok Button
$OKButton = New-Object System.Windows.Forms.Button
$OKButton.Location = New-Object System.Drawing.Point(75,120)
$OKButton.Size = New-Object System.Drawing.Size(75,23)
$OKButton.Text = 'OK'
$OKButton.DialogResult = [System.Windows.Forms.DialogResult]::OK
$form.AcceptButton = $OKButton
$form.Controls.Add($OKButton)

#keep on top
$form.Topmost = $true

#show form as dialog
$result = $form.ShowDialog()

if($result = [System.Windows.Forms.DialogResult]::OK)
{
    #this tells it to get the Name of the property and not just the Item
    $selectedComputer = $listBox.SelectedItem.CompName    
    Restart-Computer -ComputerName $selectedComputer -Credential Get-Credential Domain\Username -Force
}

Note: if you use the Active Directory query your computers must all have a Name and Description attribute (unless of course you plan on handling empty/null values)