Supress error in powershell and display custom error message - powershell

Question

I have created a PowerShell script that will add a VPN connection for Cisco Meraki.
The script itself functions as intended, but if a error occures, the "Completed" popup appears, with the error message shown in the PS windows.
Is it possible to supress the error and show a custom error popup based on the error that appears, while stopping the "Completed" popup from appearing?
I am aware of the $ErrorActionPreference= 'silentlycontinue', but unsure of how to implement this with a custom error.
Script to add VPN connections for Cisco Meraki.
$Name = Read-Host -Prompt 'Enter the profile name for this VPN connection'
$password = Read-Host -assecurestring "Please enter your Pre-shared Key"
$password = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto([System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($password))
Add-VpnConnection -Name "$Name" -ServerAddress 193.214.153.2 -AuthenticationMethod MSChapv2 -L2tpPsk "$password" -TunnelType L2tp -RememberCredential -Force
$wshell = New-Object -ComObject Wscript.Shell
$wshell.Popup("VPN-profile for $Name has been created.
You may now use this connection.
Username and password is required on first time sign on.
Support: _witheld_ | _witheld_",0,"Completed")

Answer 1

Since your script continues to run after the error occurs, you are dealing with a non-terminating error, so you can use the -ErrorVariable common parameter to capture a given cmdlet invocation's error(s).
Using a simplified example, which you can apply analogously to your Add-VpnConnection call:
# Call Get-Item with a nonexistent path, which causes a *non-terminating* error.
# * Capture the error with -ErrorVariable in variable $err.
# * Suppress the error console output with -ErrorAction SilentlyContinue
Get-Item /NoSuch/Path -ErrorVariable err -ErrorAction SilentlyContinue
$null = (New-Object -ComObject Wscript.Shell).Popup(
$(if ($err) { "Error: $err" } else { 'Success.' })
)
If you were dealing with a terminating error, you'd have to use try / catch:
# Call Get-Item with an unsupported parameter, which causes a
# *(statement-)terminating* error.
try {
Get-Item -NoSuchParam
} catch {
# Save the error, which is a [System.Management.Automation.ErrorRecord]
# instance. To save just a the *message* (a string), use
# err = "$_"
$err = $_
}
$null = (New-Object -ComObject Wscript.Shell).Popup(
$(if ($err) { "Error: $err" } else { 'Success.' })
)
Note:
Neither -ErrorAction nor -ErrorVariable work with terminating errors.
Conversely, try / catch cannot be used to handle non-terminating errors, which is presumably why Ranadip Dutta's answer didn't work for you.
For a comprehensive discussion of PowerShell error handling, see this GitHub issue.

Answer 2

You have to have the error handling for the script. I have given it as a whole in the below script but you can configure it based on your need:
try
{
$Name = Read-Host -Prompt 'Enter the profile name for this VPN connection'
$password = Read-Host -assecurestring "Please enter your Pre-shared Key"
$password = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto([System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($password))
Add-VpnConnection -Name "$Name" -ServerAddress 193.214.153.2 -AuthenticationMethod MSChapv2 -L2tpPsk "$password" -TunnelType L2tp -RememberCredential -Force
$wshell = New-Object -ComObject Wscript.Shell
$wshell.Popup("VPN-profile for $Name has been created.You may now use this connection.Username and password is required on first time sign on.Support: _witheld_ | _witheld_",0,"Completed")
}
catch
{
"Your custom message"
$_.Exception.Message
}
For further refence, read TRY/CATCH/FINALLY in Powershell
Hope it helps.