PSMonday #22: September 26, 2016

Topic: Get-Member Continued IV

Notice: This post is a part of the PowerShell Monday series — a group of quick and easy to read mini lessons that briefly cover beginning and intermediate PowerShell topics. As a PowerShell enthusiast, this seemed like a beneficial way to ensure those around me at work were consistently learning new things about Windows PowerShell. At some point, I decided I would share these posts here, as well. Here’s the PowerShell Monday Table of Contents.

Now that we’ve had a brief introduction to arrays, let’s quickly get back and discuss the difference of piping to Get-Member, and not piping to Get-Member. Let’s begin by creating a new array, but this time, we’ll make sure it’s holding both string and integer values.

$array = 1,'string1',2,'string2'
$array

1
String1
2
String2

Let’s pipe this to Get-Member. I’ve modified the below command, so it takes up less space; I’m only returning the TypeName. I’ve also included the -Unique parameter as a part of the Select-Object command. Without it, it would return the TypeName for each of the properties and methods. Try it without, and see what I mean.

$array | Get-Member | Select-Object TypeName -Unique

TypeName
--------
System.Int32
System.String

When we pipe to Get-Member, we get a result for each of the different types of objects in the array. Although our array has four total values, there’s still only two different types of objects: integer and string.

Let’s set up the next command, but this time we’ll use Get-Member without piping.

Get-Member -InputObject $array | Select-Object TypeName -Unique

TypeName
--------
System.Object[]

Notice that there’s nothing about integers or strings. In this next example, we’ll apply one of the methods. I happen to know there’s a method called GetType that will provide a bit more information about our $array variable. If you didn’t know about the GetType method, you could’ve removed the pipe and Select-Object command, to see all of the available properties and methods, and tested some out.

(Get-Member -InputObject $array).GetType()

IsPublic IsSerial Name                  BaseType
-------- -------- ----                  --------
True     True     Object[]              System.Array

Based on the above results, you can see that PowerShell knows that this is an array. So what’s all this mean? It means that when we don’t pipe to Get-Member, we evaluated the variable as a whole — whatever it might be. When we pipe to Get-Member, we’re evaluating the type of each element contained in the array, or rather, each object in a collection.

The pipeline in PowerShell is used for much more than Get-Member, but the concept is the same. Each object has a turn to go across, or through, the pipeline, in order to be evaluated. This is a key concept and I’m sure we’ll see it in the future, in topics unrelated to the Get-Member cmdlet.

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