Remove Object from SCOM Console on Termination.ps1

#INPUTS
#$ENV:SCOM_MGMT_SERVER = IP Address or FQDN of SCOM Management Server
#$ENV:SCOM_MGMT_GROUP = SCOM Management Group, if NULL, attempt to determine via registry
#$ENV:SCOM_USERNAME = User that has access to connect remotely to SCOM Management Server and has access to delete managed computers
#$ENV:SCOM_PASSWORD = Password for above user

#Set Error Action Preference
$errorActionPreference = "Stop"

#RightLink/RSC Working Directory
$rightlink_dir = 'C:\Program Files\RightScale\RightLink'

#Decommission Reason
$decom_reason = & "${rightlink_dir}\rsc.exe" rl10 show /rll/proc/shutdown_kind

If ($decom_reason -eq "terminate") {
    
    Write-Output "Instance is terminating. Delete managed computer from SCOM..."

    #SCOM Management Server
    $mgmtServer = $ENV:SCOM_MGMT_SERVER

    #SCOM Management Group
    if($ENV:SCOM_MGMT_GROUP) {
        $mgmtGroup = $ENV:SCOM_MGMT_GROUP
    }
    else {
        $mgmtGroup = Get-ChildItem -Path “HKLM:\SYSTEM\CurrentControlSet\Services\HealthService\Parameters\Management Groups\” -ErrorAction SilentlyContinue | ForEach-Object {Get-ItemProperty $_.pspath | select -expandproperty PSChildName}
        if (!($mgmtGroup)) {
            Write-Output "Error! Unable to automatically determine Management Group!"
            EXIT 1
        }
        elseif ($mgmtGroup.Count -gt 1) {
            Write-Output "Error! Unable to automatically determine Management Group as more then one were discovered!"
            Write-Output "Discovered Management Groups: $mgmtGroup"
            EXIT 1
        }
        else {
            Write-Output "Management Group: $mgmtGroup"
        }

    }

    #Current instance/server FQDN
    $dnsHostName = (Get-WmiObject win32_computersystem).DNSHostName+"."+(Get-WmiObject win32_computersystem).Domain

    #SCOM Management Server and Management Group credentials
    $scomPassword = $ENV:SCOM_PASSWORD | ConvertTo-SecureString -AsPlainText -Force
    $scomCreds = New-Object System.Management.Automation.PSCredential -ArgumentList $ENV:SCOM_USERNAME, $scomPassword

    #Connect to SCOM Management Server and delete managed computer
    Invoke-Command -ComputerName $mgmtServer -Credential $scomCreds -ScriptBlock {
    
        [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.EnterpriseManagement.OperationsManager.Common")
        [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.EnterpriseManagement.OperationsManager")

        $mgConnSetting = New-Object Microsoft.EnterpriseManagement.ManagementGroupConnectionSettings("$Using:mgmtGroup")
        $mg = New-Object Microsoft.EnterpriseManagement.ManagementGroup($mgConnSetting)
        $admin = $mg.Administration
        $agentManagedComputerType = [Microsoft.EnterpriseManagement.Administration.AgentManagedComputer];
        $genericListType = [System.Collections.Generic.List``1]
        $genericList = $genericListType.MakeGenericType($agentManagedComputerType)
        $agentList = New-Object $genericList.FullName

        #Replace DNSHostName with FQDN of agent to be deleted.
        #ComputerName is a SCOM management server to query
        $agent = Get-SCOMAgent -DNSHostName $Using:dnsHostName -ComputerName $Using:mgmtServer
        $agentList.Add($agent);
        $genericReadOnlyCollectionType = [System.Collections.ObjectModel.ReadOnlyCollection``1]
        $genericReadOnlyCollection = $genericReadOnlyCollectionType.MakeGenericType($agentManagedComputerType)
        $agentReadOnlyCollection = New-Object $genericReadOnlyCollection.FullName @(,$agentList);

        $admin.DeleteAgentManagedComputers($agentList)

    }
}
else {

    Write-Output "Instance is rebooting. Skipping SCOM deletion."

}