Powershell ForEach-Object: You cannot call a method on a null-valued expression - azure

Question

I am trying to extract the tag values for SystemOwner and TechnicalOwner.
However I get the error "ForEach-Object: You cannot call a method on a null-valued expression"
I already know that the "$Tags = $RG.Tags" could be the issue because running this variable does not give me any results. Then how do I get the resource group tags?
$RGs = (Get-AzResourceGroup).ResourceGroupName
ForEach-Object $RG in $RGs
{
# Get email address value for each SystemOwner and TechnicalOwner Tag in the RG
$Tags = $RG.Tags
$TO = ($Tags.GetEnumerator() | Where-Object {$_.Key -eq "Technical*"}).value
If ($TO)
{
if ($TO.Value -ne $null) {
Write-Host "Technical Owner Found in the Resource Group, building an Array"
$contactemailadress += $TO.Value
}
}
$SO = $Tags.GetEnumerator() | Where-Object {$_.Key -eq "SystemOwner"} #looking for Resource Group tag Names that have a space in the name
If ($SO)
{
if ($SO.Value -ne $null) {
Write-Host "System Owner Found in the Resource Group, building an Array"
$contactemailadress += $SO.Value
}
}
}

Answer 1

I think you could do something like this:
$contactemailadress = #()
$RGs = Get-AzResourceGroup
$RGs | ForEach-Object {
# Get email address value for each SystemOwner and TechnicalOwner Tag in the RG
$Tags = $_.Tags
If ($Tags -and $Tags['TechnicalOwner'])
{
Write-Host "Technical Owner Found in the Resource Group, building an Array"
$contactemailadress += $Tags['TechnicalOwner']
}
If ($Tags -and $Tags['SystemOwner'])
{
Write-Host "System Owner Found in the Resource Group, building an Array"
$contactemailadress += $Tags['SystemOwner']
}
}
The main issue you have is that (Get-AzResourceGroup).ResourceGroupName returns the Resource Group Name - however, in order for the tags to be returned you would need the full object.
You can prove this by checking for Properties on the Get-AzResourceGroup command you are running:
(Get-AzResourceGroup -Name resource_group_name).ResourceGroupName | Get-Member -Type Property
TypeName: System.String
Name MemberType Definition
---- ---------- ----------
Length Property int Length {get;}
As you can see, this command only has one property - length, which is not useful for your scripts purpose.
If you run this instead, you get the full object with all properties:
Get-AzResourceGroup -Name resource_group_name | Get-Member -Type Property
TypeName: Microsoft.Azure.Commands.ResourceManager.Cmdlets.SdkModels.PSResourceGroup
Name MemberType Definition
---- ---------- ----------
Location Property string Location {get;set;}
ManagedBy Property string ManagedBy {get;set;}
ProvisioningState Property string ProvisioningState {get;set;}
ResourceGroupName Property string ResourceGroupName {get;set;}
ResourceId Property string ResourceId {get;set;}
Tags Property hashtable Tags {get;set;}
TagsTable Property string TagsTable {get;}
You can use foreach or ForEach-Object, both should work but when using the latter you can query the variable inside the loop using the $_ notation.
Lastly, in your script there seem to be some variables unnecessarily used (but I don't know if you would need them later on), such as $TO and two if-statements that more or less do the same (i.E. If ($SO) and if ($SO.Value -ne $null)).