It's time to make an exception

[JulianMilano]

My script logs into the CIMC of my Cisco servers to gather hardware information. There's one particular server which it seems the CIMC is not responding and instead of getting a "unable to connect" error from PowerShell, I'm getting

Write-Host "$StringLabel Error: $($PSItem.ToString())"
[MyServerName/172.2.12.167 Error: Object reference not set to an instance of an object.

I'm having difficulty capturing this exception. When I query the Exception type, I get:

$Error[0].Exception.GetType().FullName
System.NullReferenceException

However my Catch [System.NullReferenceException] statement is not picking it up. Instead my [System.Exception] Catch is picking it up?

Code is:

    Try
        {
        # Let's connect to the CIMC.
        $Connected = $True
        Write-Host "$StringLabel Attempting a connection to server IMC." -ForegroundColor Yellow
        $IMCHandle = Connect-IMC -Name $RackServerIMCIP -Credential $IMCServerCredential -NotDefault -ErrorAction Stop
        }

    Catch [System.NullReferenceException]
        {
        Write-Host "$StringLabel Error: $($PSItem.ToString())" -ForegroundColor Red
        $Connected = $False
        $ErrorPropertyValue = "Null Reference Error"
        }

    Catch [System.Exception]
        {
        # Did not connect due to connection issue.
        Write-Host "$StringLabel Error: $($PSItem.ToString())" -ForegroundColor Red
        If ($PSItem.Exception.ToString().Contains("Unable to connect"))
            {
            # Set connection flag false.
            $Connected = $False
            $ErrorPropertyValue = "Not Connected"
            }
        Else
            {
            $Connected = $False
            $ErrorPropertyValue = "System Exception"
            Write-Host "Not a connection issue." -ForegroundColor Red
            }
        }
    Catch
        {
        Write-Host "$StringLabel Error: $($PSItem.ToString())" -ForegroundColor Red
        $Connected = $False
        $ErrorPropertyValue = "Unknown Error"
        }

What am I doing wrong?

[#2 · Accepted solution]

@JulianMilano 

I can't see anything wrong with your code.

The only thing that makes sense to me is that the thrown exception is not actually of the type [System.NullReferenceException], but since I can't replicate your scenario, I'm simply making an educated guess.

From a diagnostic perspective, I'd verify the exception's type inheritance manually using:

try
{
    Connect-IMC -Name $RackServerIMCIP -Credential $IMCServerCredential -NotDefault -ErrorAction:Stop
}
catch
{
    $_.Exception.pstypenames;
}

Where the top-most type name is the most specific to the exception, becoming less so as you read downwards.

Here's a simple example to illustrate the output:

Cheers,

Lain

[#3]

Thanks Lain- that last one opens up the problem really nicely!