PowerShell 3 Dimensional Arrays

Recently I worked on a PowerShell script to extend hardware inventory. During this process, I needed a named array with three elements. I will admit that I have never taken a programming class. However, I know the fundamentals of object-orientation programming and have become very good at PowerShell. However, hunting on the Internet is my go-to reference when it comes to some fundamentals. As we all know, the key to finding the correct answer on the Internet is finding the right keywords. First, I tried “3-dimensional array, hash tables, PowerShell arrays,” but that did not work. Finally, I found an excellent blog by Tommy Maynard, “There is a Difference: Arrays Versus Hash Tables.” The blog explains the differences between arrays and hash tables. I have used hash tables in the past, and I admit the “GetEnumerator()” function has confused me.

While this information was helpful, I wanted an object with three properties: UserID, LogonDate, and LogoffDate. Redefining the problem from an array with three elements to an object with three properties led me to the solution. What I needed to create was a new custom object. Yes, I know this is obvious now, but last night it was not, hence the need for this blog to remind me of the answer so I can refer to it in the future.

The command is “New-Object System.Collections.ArrayList”. Below is the code snippet.

#Create an Array with properties (Column Headers)

#Define an array list object.
$LogonList = New-Object System.Collections.ArrayList 

#Create a function to add the members to the array
function Add-ArrayListMember ($UserName, $LastLogon, $LastLogoff, $ListName)  
    $item=New-Object System.Object
    $item | Add-Member -MemberType NoteProperty -Name "UserID" -Value $UserName
    $item | Add-Member -MemberType NoteProperty -Name "LogOnDate" -Value $LastLogon
    $item | Add-Member -MemberType NoteProperty -Name "LogOffDate" -Value $LastLogoff
    $ListName.Add($item) | Out-Null

#call the function to add members to the array
Add-ArrayListMember -UserName User1 -LastLogon "10/11/2021" -LastLogoff "12/10/2021" -ListName $LogonList
Add-ArrayListMember -UserName User2 -LastLogon "1/12/2022" -LastLogoff "1/30/2021"  -ListName $LogonList
Add-ArrayListMember -UserName User3 -LastLogon "4/14/2022" -LastLogoff "5/1/2022"  -ListName $LogonList

#Perform a Get-Member command to view the properties of the new object.

PS C:\Users\dawn> $LogonList |gm

   TypeName: System.Object

Name        MemberType   Definition                    
----        ----------   ----------                    
Equals      Method       bool Equals(System.Object obj)
GetHashCode Method       int GetHashCode()             
GetType     Method       type GetType()                
ToString    Method       string ToString()             
LogOffDate  NoteProperty string LogOffDate=12/10/2021  
LogOnDate   NoteProperty string LogOnDate=10/11/2021   
UserID      NoteProperty string UserID=User1    

# the last three members of the object are the properties added in the function

PS C:\Users\dawn> $LogonList

UserID LogOnDate  LogOffDate
------ ---------  ----------
User1  10/11/2021 12/10/2021
User2  1/12/2022  1/30/2021 
User3  4/14/2022  5/1/2022 

As denoted in the Get-Member command, LogonList is a System Object with LogOffDate, LogOndate, and userID as members. Now that I had an object with three members, I created a WMI class and populated it with each instance of user logon.





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