PowerShell SMO Error Handling Empty or Null

Question

I have a script that gets SQL Server properties using SMO. I have the script display the properties out in html but I am having trouble setting it up so that the script still enters a datarow even when the SMO object returns empty because of a connection or other error. How would I get it to enter a string into the data row if the SMO object returns empty or null?

I have already tried an If statement where $serverObject -eq $null and that didn't print it out.

foreach($instance in $instanceList)
{        
    $serverObject = New-Object Microsoft.SqlServer.Management.Smo.Server($instance)

    $instance = $instance.toupper()

    $serverName = $serverObject.ComputerNamePhysicalNetBIOS;
    $instanceName = $serverObject.InstanceName;
    $versionBuild = $serverObject.Information.ResourceVersion;
    $servicePack = $serverObject.Information.ProductLevel;

    $color = $redColor;

    if($serverName -eq $null -and $instanceName -eq $null)
    {
        [string]$serverName = "Error Connecting"
        $instanceName = $instance
    }
        else
        {
            if($instanceName -eq $null -and $versionBuild -eq $null)
            {
                [string]$instanceName = $instance
                [string]$versionBuild = "Error"
            }
        }
    }

    # Set background color to green if service pack is 2008r2 SP2
    if($versionBuild -match $vs2008r2sp2)
    {
        $color = $greenColor
    }          
    else
    {    
        # Set background color to yellow if service pack is 2008 SP3
        if($versionBuild -match $vs2008sp3)
        {
                $color = $yellowColor
        }
        else
        {
            # Set background color to orange if service pack is 2005 SP4
            if($versionBuild -match $vs2005sp4)
            {
                $color = $orangeColor   
            }
        }
    }

    # Create table data rows 
    $dataRow = "
    <tr>
        <td width='10%'>$serverName</td>
        <td width='15%'>$instanceName</td>                        
        <td width='5%' bgcolor=`'$color`' align='center'>$versionBuild</td>
        <td width='10%' align='center'>$servicePack</td>
    </tr>
    "

    # If statement needed to remove label that were null
    If ($versionBuild -ne 'NaN') 
    {
        Add-Content $servicePackReport $dataRow;
        Write-Host -ForegroundColor DarkYellow "$serverName $instanceName service pack build = $versionBuild";
        $i++        
    }
}

Answer 1

You are getting into trouble because of how you are trying to check to see if the instance exists. You do the check, but then you set the variables to "Error". This causes problems because later on you want to check $versionBuild as your evaluation if the instance is valid. This is where the error is. You are evaluating:

If ($versionBuild -ne 'NaN')

The problem is that you are comparing if it is not equal to the string "NaN". If the $versionBuild is $null (i.e. when the instance does not exist), that is not equal to "NaN", so write the row. To fix it, change it to:

If ($versionBuild -ne $null)

But besides that, you can simplify things, and increase the speed a bit by checking if the instance exists first. If it does, -then- you pull all the rest of the information and create your data row.

If it doesn't exist, then you just have it spit out an error message.

foreach($instance in $instanceList)
{        
    $serverObject = New-Object Microsoft.SqlServer.Management.Smo.Server($instance)

    $instance = $instance.toupper()

    $serverName = $serverObject.ComputerNamePhysicalNetBIOS;

    #Check to see if the instance exists
    if($serverName -ne $null)
    {
        #The instance Exists, get the rest of the properties
        $instanceName = $serverObject.InstanceName;
        $versionBuild = $serverObject.Information.ResourceVersion;
        $servicePack = $serverObject.Information.ProductLevel;

        $color = $redColor;
        # Set background color to green if service pack is 2008r2 SP2
        if($versionBuild -match $vs2008r2sp2)
        {
        $color = $greenColor
        }          
        else
        {    
        # Set background color to yellow if service pack is 2008 SP3
        if($versionBuild -match $vs2008sp3)
        {
            $color = $yellowColor
        }
        else
        {
            # Set background color to orange if service pack is 2005 SP4
            if($versionBuild -match $vs2005sp4)
            {
            $color = $orangeColor   
            }
        }
        }

        # Create table data rows 
        $dataRow = "
        <tr>
        <td width='10%'>$serverName</td>
        <td width='15%'>$instanceName</td>                        
        <td width='5%' bgcolor=`'$color`' align='center'>$versionBuild</td>
        <td width='10%' align='center'>$servicePack</td>
        </tr>
        "

        Add-Content $servicePackReport $dataRow;
        Write-Host -ForegroundColor DarkYellow "$serverName $instanceName service pack build = $versionBuild";
        $i++        
    }
    else
    {
       #The instance does not exist. Write error message to console
       Write-Host -ForegroundColor Red "$instance Does NOT exist";
    }

}