DynamicObjectPerformanceTest.ps1

cls
Write-Verbose "$(Get-Date): Getting DIR information..." -Verbose
$Dir = "C:\dropbox\test"
$Files = Get-ChildItem $Dir -File -Recurse | Select FullName,BaseName,Length
Write-Verbose "$(Get-Date): $($Files.Count) files found" -Verbose

Write-Verbose "$(Get-Date): Using calculated fields in Select..." -Verbose
Measure-Command {
    $Files | Select Fullname,BaseName,Length,@{Name="SizeMB";Expression={ [math]::Round($_.Length / 1MB,2) }},@{Name="SizeGB";Expression={ [math]::Round($_.Length / 1GB,2) }}
}


Write-Verbose "$(Get-Date): Now calculating with dynamic properties..." -Verbose
Measure-Command {
    $Files | 
        Add-Member -MemberType ScriptProperty -Name SizeMB -Value { [math]::Round($this.Length / 1MB,2) } -PassThru | 
        Add-Member -MemberType ScriptProperty -Name SizeGB -Value { [math]::Round($this.Length / 1GB,2) }
    $Files
}
Write-Verbose "$(Get-Date): Done!" -Verbose