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powershellpowershell-3.0

How Does Member Enumeration Work in PowerShell 3?

In PoweShell 2 we did:

Get-ChildItem | ForEach-Object {$_.LastWriteTime} | Sort-Object

In Powershell 3 we do:

(Get-ChildItem).LastWriteTime | Sort-Object

But how does it work, i read this blog post on MSDN and they say that its faster because the foreach loop isnt running? So how does it enumerate the properties then ?

Solution

  • PowerShell is doing the hard work for us and it loops over the collection internally. I like to call this "implicit foreach". Assuming the member you specified is present on each object, if the member you specified is a property, you get back its value. If it's a method, it invokes the method on the each object.

    In v2, to get all process names you had to take care of looping yourself:

    Get-Process | Foreach-Object {$_.Name}

    In v3, the equivalent would be:

    (Get-Process).Name

    Same applies to methods. To kill all processes with name starting with note*:

    (Get-Process note*).Kill()