NotePropertiesExample.ps1

$Number = 11
$Property = [PSNoteProperty]::new("IsNumber", $true)
$Number.PSObject.Properties.Add($Property)

$Number # Gives back 11, as you'd expect
$Number | Format-List -Force # shows the hidden property

#Bonus: ScriptProperties can use $this to refer to the object they're attached to
$Number = 7
$AnotherNumber = 42

$Property = [PSScriptProperty]::new("IsEven", {$this % 2 -eq 0})
$Property2 = [PSScriptProperty]::new("Value", {$this})

$Number.PSObject.Properties.Add($Property)
$Number.PSObject.Properties.Add($Property2)
$AnotherNumber.PSObject.Properties.Add($Property)
$AnotherNumber.PSObject.Properties.Add($Property2)

$Number, $AnotherNumber | Format-Table -Force

# Add-Member example
$Object = @{"Steve", 12}
$Object | 
    Add-Member -Name "Label" -Value "Hashtable" -MemberType NoteProperty -PassThru |
    Format-Table -Force