Cannot execute same powershell function twice, gives error

Question

I'm fairly new to powershell and I'm basically writing a script which performs a join on several .csv files based on a primary column. I am using the Join-Collections script from here: http://poshcode.org/1461

As I need to combine 5 .csv files, I need to run this function 4 times.

On the first run, it works fine, but then trying to run the function again gives 'No object specified to the cmd-let' errors.

In trying to debug, I've literally copy-and-pasted the line and only changed the variable name to make a new variable.

I must be doing something fundamentally wrong...

$SumFile = "VMSummary.csv"
$MemFile = "VMMemory.csv"
$ProcFile = "VMProcessor.csv"
$OSFile = "VMOS.csv"
$NicFile = "VMNics.csv"

$SumFileCSV = Import-Csv $SumFile | Select VMElementName,GuestOS,Heartbeat,MemoryUsage,IpAddress
$MemFileCSV = Import-Csv $MemFile | Select VMElementName,Reservation
$ProcFileCSV = Import-Csv $ProcFile
$OSFileCSV = Import-Csv $OSFile
$NicFileCSV = Import-Csv $NicFile

$JoinColumn = "VMElementName"

function Join-Collections {
PARAM(
   $FirstCollection
,  [string]$FirstJoinColumn
,  $SecondCollection
,  [string]$SecondJoinColumn=$FirstJoinColumn
)
PROCESS {
   $ErrorActionPreference = "Inquire"
   foreach($first in $FirstCollection) {
      $SecondCollection | Where{ $_."$SecondJoinColumn" -eq $first."$FirstJoinColumn" } | Join-Object $first
   }
}
BEGIN {
   function Join-Object {
   Param(
      [Parameter(Position=0)]
      $First
   ,
      [Parameter(ValueFromPipeline=$true)]
      $Second
   )
   BEGIN {
      [string[]] $p1 = $First | gm -type Properties | select -expand Name
   }
   Process {
      $Output = $First | Select $p1
      foreach($p in $Second | gm -type Properties | Where { $p1 -notcontains $_.Name } | select -expand Name) {
         Add-Member -in $Output -type NoteProperty -name $p -value $Second."$p"
      }
      $Output
   }
   }
}
}

$Temp = Join-Collections $SumFileCSV $JoinColumn $MemFileCSV $JoinColumn

$Temp

##BREAKS HERE
$Temp2 = Join-Collections $SumFileCSV $JoinColumn $MemFileCSV $JoinColumn

UPDATE

It gives the following error:

No object has been specified to the get-member cmdlet
+ foreach($p) in $Second | gm <<<<  -type Properties | Where { $p1 -notcontains     $_.Name } | select -expand Name)

The csv data is pretty straight forward. When I print out $Temp just before it breaks, it spits out:

GuestOS       : Windows Server (R) 2008 Standard
Heartbeat     : OK
IpAddress     : 192.168.48.92
MemoryUsage   : 1024
VMElementName : VM015
Reservation   : 1024

GuestOS       : Windows Server (R) 2008 Standard
Heartbeat     : OK
IpAddress     : 192.168.48.151
MemoryUsage   : 1028
VMElementName : VM053
Reservation   : 1028

GuestOS       : Windows Server (R) 2008 Standard
Heartbeat     : OK
IpAddress     : 192.168.48.214
MemoryUsage   : 3084
VMElementName : VM065
Reservation   : 3084

GuestOS       : 
Heartbeat     : 
IpAddress     : 
MemoryUsage   : 
VMElementName : VM074
Reservation   : 1024

GuestOS       : Windows Server 2008 R2 Standard
Heartbeat     : OK
IpAddress     : 192.168.48.32
MemoryUsage   : 3072
VMElementName : VM088
Reservation   : 3072

GuestOS       : Windows Server (R) 2008 Enterprise
Heartbeat     : OK
IpAddress     : 192.168.48.81
MemoryUsage   : 3084
VMElementName : VM090
Reservation   : 3084

GuestOS       : Windows Server 2008 R2 Enterprise
Heartbeat     : OK
IpAddress     : 192.168.48.82
MemoryUsage   : 5120
VMElementName : VM106
Reservation   : 5120

The rest of the .csv data is the same sort of stuff - just stats on different servers.

Ideally what I want to do is this :

$Temp = Join-Collections $SumFileCSV $JoinColumn $MemFileCSV $JoinColumn

$Temp = Join-Collections $Temp $JoinColumn $ProcFileCSV $JoinColumn

$Temp = Join-Collections $Temp $JoinColumn $OSFileCSV $JoinColumn

$Temp = Join-Collections $Temp $JoinColumn $NicFileCSV $JoinColumn | Export-Csv "VMJoined.csv" -NoTypeInformation -UseCulture

What error does it give? Also post examples of you CSV data you are merging. — Andy Arismendi
– Andy Arismendi, Commented Jan 27, 2012 at 5:23

jon Z · Accepted Answer · 2012-01-27 10:26:26Z

This code works fine on Powershell v3 CTP 2 (which is probably what @manojlds is using). In Powershell V2 however the parameter $second of the Join-Object function is not bound when invoking Join-Collections the second time. This can be easily verified by adding the following line to the process block inside the Join-Object function:

$psboundparameters | out-host

You will notice that when invoking Join-Collections for the first time both parameters (of Join-Object are bound, however the second time $second is no longer bound.

It is unclear what is causing this behaviour, but since it seems to be working in Powershell V3 I'm guessing it's a bug.

To make the function work in Powershell V2 one could explicitly bind the parameters by replacing this line:

$SecondCollection | Where{ $_."$SecondJoinColumn" -eq $first."$FirstJoinColumn" } | Join-Object $first

by this line:

$SecondCollection | Where{ $_."$SecondJoinColumn" -eq $first."$FirstJoinColumn" } | %{Join-Object -first $first -second $_}

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