Since I did my last post on snapshots I have gotten several comments and few e-mails asking how to map ReturnValues to actual human readable strings.  I guess not every one just knows that 32773 is Invalid Parameter…  Well after many hours of asking and playing I have the answer – or at least a good start so here it is:

The real magic is this in ProcessWMIJob… it now operates on the pipeline and can take two new parameters one for the WmiClassPath and a second for the MethodName…  It uses those to retrieve the error strings for the specific class and function from WMI…  To use this just put it at the top of your scripts or in your environment and party on…

filter ProcessWMIJob

   
param
    ( 
        [
string]$WmiClassPath = $null,
        [
string]$MethodName = $null
    )
    
   
$errorCode = 0

   
if ($_.ReturnValue -eq 4096)
    { 
       
$Job = [WMI]$_.Job

       
while ($Job.JobState -eq 4)
        { 
           
Write-Progress $Job.Caption "% Complete" -PercentComplete $Job.PercentComplete
           
Start-Sleep -seconds 1
           
$Job.PSBase.Get()
        } 
       
if ($Job.JobState -ne 7)
        { 
           
if ($Job.ErrorDescription -ne "")
            {
               
Write-Error $Job.ErrorDescription
               
Throw $Job.ErrorDescription
            }
           
else
            {
               
$errorCode = $Job.ErrorCode
            }
        } 
       
Write-Progress $Job.Caption "Completed" -Completed $TRUE
    }
   
elseif($_.ReturnValue -ne 0)
    {
       
$errorCode = $_.ReturnValue
    }
    
   
if ($errorCode -ne 0)
    { 
       
Write-Error "Hyper-V WMI Job Failed!"
       
if ($WmiClassPath -and $MethodName)
        {
           
$psWmiClass = [WmiClass]$WmiClassPath
           
$psWmiClass.PSBase.Options.UseAmendedQualifiers = $TRUE
           
$MethodQualifiers = $psWmiClass.PSBase.Methods[$MethodName].Qualifiers
           
$indexOfError = [System.Array]::IndexOf($MethodQualifiers["ValueMap"].Value, [string]$errorCode)
           
if ($indexOfError -ne "-1")
            {
               
Throw "ReturnCode: ", $errorCode, " ErrorMessage: '", $MethodQualifiers["Values"].Value[$indexOfError], "' - when calling $MethodName"
            }
           
else
            {
               
Throw "ReturnCode: ", $errorCode, " ErrorMessage: 'MessageNotFound' - when calling $MethodName"
            }
        }
       
else
        {
           
Throw "ReturnCode: ", $errorCode, "When calling $MethodName - for rich error messages provide classpath and method name."
        }
    } 
   
return $_
}

Example:

$VHDService = get-wmiobject -class "Msvm_ImageManagementService" -namespace "root\virtualization"
$VHDService.CreateDynamicVirtualHardDisk("C:\Users\Public\Documents\Hyper-V\Virtual hard disks\MyVHD.vhd", 20GB) | ProcessWMIJob $VHDService "CreateDynamicVirtualHardDisk"

Revised 7/6 To Add Support For WMI Jobs that have blank Error Descriptions.
Revised 7/28 To Return Created Object on Success and To Add Sample Code...

Taylor Brown
Hyper-V Integration Test Lead
http://blogs.msdn.com/taylorb

clip_image001