Try Catch - How to Catch error but continue? - powershell

Question

I've got this script, which loops through a foreach loop for each computer, and for each computer it loops through each NIC. Currently the Catch block is not running. What I want to do is catch the error (usually because get-wmi is not able to connect to a machine), do something (add some information to a PSCustomObject), but then continue to the next iteration. How do I catch an error but also continue the foreach loop?
param (
[Alias('Hostname')]
[string[]]$ComputerName = #('pc1','pc2'),
$OldDNSIP = '7.7.7.7',
$NewDNSIP = #('9.9.9.9','8.8.8.8')
)
$FailedArray = #()
$DHCPArray = #()
Foreach ($Computer in $ComputerName){
$NICList = Get-WmiObject Win32_NetworkAdapterConfiguration -computername $Computer | where{$_.IPEnabled -eq "TRUE"}
Foreach($NIC in $NICList){
If($NIC.DHCPEnabled -eq $false){
Try{
$DNSIPs = $NIC.DNSServerSearchOrder
if($DNSIPs -contains $OldDNSIP){
$NewDNS = $DNSIPs | foreach {$_ -replace $OldDNSIP,$NewDNSIP[0]}
$null = $NIC.SetDNSServerSearchOrder($NewDNS)
}
else{
write-host " - Old DNS server IP not found... ignoring"
}
}
Catch{
write-host " - Something went wrong... logging to a CSV for review later" -ForegroundColor Red
$FailedArray += [PSCustomObject]#{
'Computer' = $Nic.pscomputername
'NIC_ID' = $nic.index
'NIC_Descrption' = $nic.description}
}
}
ElseIf($NIC.DHCPEnabled -eq $true){
write-host " - DHCP is enabled. Adding this IP, Hostname, Nic Index and DHCP Server to a CSV for reviewing."
#add pscomputer, nic id, refernece and dhcp server to DHCPNICArray
$DHCPArray += [PSCustomObject]#{
'Computer' = $Nic.pscomputername
'NIC_ID' = $nic.index
'NIC_Descrption' = $nic.description
'DHCPEnabled' =$nic.dhcpenabled
'DHCPServer' = $nic.dhcpserver}
}
}
}
$DHCPArray | export-csv c:\temp\dhcp.csv -NoTypeInformation
$FailedArray | export-csv c:\temp\failed.csv -NoTypeInformation

Answer 1

If the WMI errors are due to a connection fail, they will occur before any of the nics are processed. If you want to catch them, and then continue with the next computer, you have to move the try-catch up to the level of that loop. If you also want to catch nic-specific errors, you need a 2nd try-catch at that level.
Also, consider using -ErrorAction Stop parameter, or specify $ErrorActionPreference = 'Stop', to make sure all errors are terminating (that means, jump right to the catch block).
Here's an example, with comments for explanation:
$ErrorActionPreference = 'Stop'
foreach ($Computer in $ComputerName) {
# add a try-catch per computer,
# to catch WMI errors
# and then continue with the next computer afterwards
try {
# if errors occur here,
# execution will jump right to the catch block the bottom
$NICList = Get-WmiObject Win32_NetworkAdapterConfiguration -ComputerName $Computer -ErrorAction Stop | where {
$_.IPEnabled -eq "TRUE"
}
foreach ($NIC in $NICList) {
# add a try-catch per NIC,
# to catch errors with this specific NIC and then
# continue with the next nic
try {
if ($NIC.DHCPEnabled -eq $false){
$DNSIPs = $NIC.DNSServerSearchOrder
if ($DNSIPs -contains $OldDNSIP) {
$NewDNS = $DNSIPs | foreach {$_ -replace $OldDNSIP,$NewDNSIP[0]}
$null = $NIC.SetDNSServerSearchOrder($NewDNS)
}
else {
write-host " - Old DNS server IP not found... ignoring"
}
}
elseif ($NIC.DHCPEnabled -eq $true){
write-host " - DHCP is enabled. Adding this IP, Hostname, Nic Index and DHCP Server to a CSV for reviewing."
$DHCPArray += [PSCustomObject]#{
'Computer' = $Nic.pscomputername
'NIC_ID' = $nic.index
'NIC_Descrption' = $nic.description
'DHCPEnabled' =$nic.dhcpenabled
'DHCPServer' = $nic.dhcpserver
}
}
}
catch {
write-host " - Configuring a NIC went wrong... logging to a CSV for review later" -ForegroundColor Red
# add nic-specific entry
$FailedArray += [PSCustomObject]#{
'Computer' = $Nic.pscomputername
'NIC_ID' = $nic.index
'NIC_Descrption' = $nic.description
}
}
# continue with next nic...
} # foreach nic
}
catch {
write-host " - Something else went wrong... logging to a CSV for review later" -ForegroundColor Red
# add entry for current computer
# (we don't know about nics, because wmi failed)
$FailedArray += [PSCustomObject]#{
'Computer' = $Computer
}
}
# continue with next computer...
} # foreach computer