Avatar of Pete Long
Pete Long
Flag for United Kingdom of Great Britain and Northern Ireland asked on

Cannot index into a null array?

More PowerShell Questions


Ive got this

#Create NIC (called MyNicName)
$nicName = "myNicName"
$nic = New-AzureRmNetworkInterface -Name $nicName `
   -ResourceGroupName $rgName `
   -Location $location -SubnetId $azvnetworks.Subnets[0].Id `
   -PublicIpAddressId $pip.Id `
   -NetworkSecurityGroupId $aznsg.Id

Open in new window

However when I run it I get

Cannot index into a null array.
At line:1 char:1
+ $nic = New-AzureRmNetworkInterface -Name $nicName `
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : NullArray

Open in new window

That means nothing to me (sorry)

What have I done wrong?

PowershellScripting Languages

Avatar of undefined
Last Comment
Pete Long

8/22/2022 - Mon
Chinmay Patel

Hi Pete,

Any decent programming language will not let you perform operation with a null object.
You see [0] (square brackets and a number within), it is a way for programming language to inspect members of an array.

I think your variable, $azvnetworks.Subnets is not populated with a value and as it is a null indexing operation cannot be performed and hence the error.

How are you getting $azvnetworks? Can you share the complete script?


Here is an array: $azvnetworks.Subnets[0].Id
where you want element 0, (using index 0).
If the array is empty then there are no elements at all so trying to get one will fail.

First check if $azvnetworks.Subnets does hold data before using it.
Pete Long

Thank guys

I'm using these instructions


On THAT example that string is called $vnet

in my example its called $azvnetworks

Which I populated earlier by doing this;
$azvnetworks = Read-Host -Prompt 'Enter Virtual Netwotk NAME (from above);'

Open in new window

This is the best money I have ever spent. I cannot not tell you how many times these folks have saved my bacon. I learn so much from the contributors.
Pete Long

Ah OK I think I see the problem that is populated with this

$vnet = New-AzureRmVirtualNetwork `
   -Name $vnetName -ResourceGroupName $destinationResourceGroup `
   -Location $location `
   -AddressPrefix `
   -Subnet $singleSubnet

Open in new window

I dont need to create one because I already have one!! (called Main-LAN)

PowerCLI C:\Program Files (x86)\VMware\Infrastructure\vSphere PowerCLI> Get-AzureRmVirtualNetwork
WARNING: Breaking changes in the cmdlet 'Get-AzureRmVirtualNetwork' :
WARNING:  - "The output type 'Microsoft.Azure.Commands.Network.Models.PSVirtualNetwork' is changing"
 - The following properties in the output type are being deprecated :

ResourceGroupName Name     Location ProvisioningState EnableDdosProtection EnableVmProtection
----------------- ----     -------- ----------------- -------------------- ------------------
RG-Test-Lab       Main-LAN uksouth  Succeeded         False                False

Open in new window

SO I need to put that information into the Array?

If so How Do I do that (sorry Im at the limit of my PowerShell here)
Pete Long

So I would need to GET my Virtual Network (already in my script called $azvnetworks )

And feed in

-Name $azvnetworks
-Location $location (already populated)
-AddressPrefix (is the same)
-Subnet $azsubnet (already populated)

Assuming the other variables in your first script are already populated, try this:
# $rgName = ...
# $location = ...
# $aznsg = ...
# $pip = ...
$azvnetworks = Get-AzureRmVirtualNetwork -Name 'Main-LAN'
#Create NIC (called MyNicName)
$nicName = "myNicName"
$nic = New-AzureRmNetworkInterface `
	-Name $nicName `
	-ResourceGroupName $rgName `
	-Location $location `
	-SubnetId $azvnetworks.Subnets[0].Id `
	-PublicIpAddressId $pip.Id `
	-NetworkSecurityGroupId $aznsg.Id

Open in new window

Get an unlimited membership to EE for less than $4 a week.
Unlimited question asking, solutions, articles and more.
Pete Long

Hi oBda

$azvnetworks already contains 'Main-LAN"

I'm trying to write this so that it can be used for many different scenarios - having the name of my Virtual Test network in the script will negate that

(background: This script connects the VMware Center locally via PowerCLI - downloads a selected VM converts it from VMDK to VHD then uploads it into Aure and creates a VM) it's the creating the VM part I'm struggling with, everything else works ok, for each piece of information required, it lists all the options and asks you to input the one you want, thats why $aznetworks is already populated, the person running the script picked and entered it)

Would it not be better to do something like

$azvnetworkTEMP = Get-AzureRmVirtualNetwork {where name is equal to $azvnetwork}

Whatever the code would be for that?

Does that make sense?


Of course you can do that. You can either use
$azvnetworks = Get-AzureRmVirtualNetwork (Read-Host -Prompt 'Enter Virtual Netwotk NAME (from above);')

Open in new window

(and not change anything on the other lines) if you do not need the name again, or if you do
$azvnetworks = Read-Host -Prompt 'Enter Virtual Netwotk NAME (from above);'
$azvnetworksTemp = Get-AzureRmVirtualNetwork $azvnetworks

Open in new window

and then refer to that new var below that lines.
Pete Long

Hi Qlemo

Thanks for the follow up

If I do that then all the other pieces wont go into the array? will they?

-ResourceGroupName $rgName `
-Location $location `
-SubnetId $azvnetworks.Subnets[0].Id `
-PublicIpAddressId $pip.Id `
-NetworkSecurityGroupId $aznsg.Id

Forgive me Im a firewall engineer script/code is not my thing?

Your help has saved me hundreds of hours of internet surfing.

Log in or sign up to see answer
Become an EE member today7-DAY FREE TRIAL
Members can start a 7-Day Free trial then enjoy unlimited access to the platform
Sign up - Free for 7 days
Learn why we charge membership fees
We get it - no one likes a content blocker. Take one extra minute and find out why we block content.
Not exactly the question you had in mind?
Sign up for an EE membership and get your own personalized solution. With an EE membership, you can ask unlimited troubleshooting, research, or opinion questions.
ask a question
Pete Long

Thanks for putting me straight :)

$vnet = Get-AzureRmVirtualNetwork -Name $azvnetworks

Threw an error, it needs the ResourceGroupName as well

$vnet = Get-AzureRmVirtualNetwork -Name $azvnetworks -ResourceGroupName $aznsg

Thanks again