How to add a member to an existing PowerShell object? - powershell

Question

The following powershell gets an object of Computer System information:
> $o = Get-WmiObject -Class Win32_ComputerSystem -ComputerName .
> $o
# output
# Domain : somedomain.com
# Manufacturer : VMware, Inc.
# Model : VMware Virtual Platform
# Name : MYSERVER
# PrimaryOwnerName : Windows User
# TotalPhysicalMemory : 17179332608
I add a new member TotalPhysicalMemoryGB to the object $o, as follows:
> $o = Add-Member -Input $o #{TotalPhysicalMemoryGB=([math]::round($t.TotalPhysicalMemory / 1GB))} -PassThru
This appears to work as I can access the member:
> $o.TotalPhysicalMemoryGB
# output
# 16
However, when I print the whole object again, the member TotalPhysicalMemoryGB does not appear in the member list:
> $o
# output
# Domain : somedomain.com
# Manufacturer : VMware, Inc.
# Model : VMware Virtual Platform
# Name : MYSERVER
# PrimaryOwnerName : Windows User
# TotalPhysicalMemory : 17179332608
What am I doing wrong? How can I get the new member included when I print $o?

Answer 1

You don't print the whole object by just output it to the console. There is a predefined view that specifies which properties of a System.Management.ManagementObject#root\cimv2\Win32_ComputerSystem is printed.
You can get a full list of all properties by using the Format-List cmdlet:
$o | Format-List *
Now you will find your previously added property.
As a workaround, you could also manually select the properties you want to output by using the Select-Object cmdlet:
$o | Select-Object Domain, Manufacturer, Model, Name, PrimaryOwnerName, TotalPhysicalMemory, TotalPhysicalMemoryGB