Advanced Windows PowerShell Scripting Video Training

Advanced Windows PowerShell Scripting Video Training
Advanced Windows PowerShell Scripting Video Training

Friday, July 28, 2017

New Syntax for Hash Tables with Select-Object

Wow!  I am actually getting around to blogging this year.  This has been an epic year in terms of how busy I have been.  Between speaking at both the PowerShell Conferences in Europe and Asia, but also expanding my client base in Asia and the Pacific islands, I have been busy.  Oh, let’s not forget adding Windows Server 2016 classes, Security+ and my work on the Azure platform. 

OK, yes I have been busy.  At some point, what I have been learning does get spilled over into my classes and this blog.

One of the sticky points with learning PowerShell has been the creation of calculated properties with Select-Object.  To do so you need to use a hash table, associative table, or dictionary.  What you call it depends on your background.   Just remember that most IT pros who take my PowerShell classes are not programmers and have never been trained as such.  Makes for an interesting week for me.  
Below is an example of how we have been teaching calculated properties.
Get-Process |
    Select-Object -Property Name,
            Name = 'VirtMemory'
            Expression = {$PSItem.VM}

You could short hand it as such.

Get-Process |
    Select-Object -Property Name, @{N = 'VirtMemory'; E = {$PSItem.VM}}

Well, that hash table is the problem.  I have not found a way to eliminate it, but I have found a way to write it a different way.

$Hash1 = @{ 'Name' = 'VirtMemory'; Expression = {$PSItem.VM}}
Get-Process | Select-Object -Property Name, $Hash1

The idea is to break it up into multiple parts so the student can focus more on what is going on and less on the confusing syntax used with Select-Object. You can add additional calculated properties as shown below.

$Hash1 = @{ 'Name' = 'VirtMemory'; Expression = {$PSItem.VM}}
$Hash2 = @{ 'Name' = 'WorkMemory'; Expression = {$PSItem.WS}}
Get-Process | Select-Object -Property Name, $Hash1, $Hash2

This technique will not work for all.  If what you are using works for you, then continue to use your technique.  I will be introducing this syntax in my PowerShell class next week in Phoenix to gauge the class response to this technique as a step in their understanding of how to perform this very common task and understand it.