How do you export objects with a varying amount of properties? - powershell

Question

Warning - I've asked a similar question in the past but this is slightly different.
tl;dr; I want to export objects which have a varying number of properties. eg; object 1 may have 3 IP address and 2 NICs but object 2 has 7 IP addresses and 4 NICs (but not limited to this amount - it could be N properties).
I can happily capture and build objects that contain all the information I require. If I simply output my array to the console each object is shown with all its properties. If I want to out-file or export-csv I start hitting a problem surrounding the headings.
Previously JPBlanc recommended sorting the objects based on the amount of properties - ie, the object with the most properties would come first and hence the headings for the most amount of properties would be output.
Say I have built an object of servers which has varying properties based on IP addresses and NIC cards. For example;
ServerName: Mordor
IP1: 10.0.0.1
IP2: 10.0.0.2
NIC1: VMXNET
NIC2: Broadcom
ServerName: Rivendell
IP1: 10.1.1.1
IP2: 10.1.1.2
IP3: 10.1.1.3
IP4: 10.1.1.4
NIC1: VMXNET
Initially, if you were to export-csv an array of these objects the headers would be built upon the first object (aka, you would only get ServerName, IP1, IP2, NIC1 and NIC2) meaning for the second object you would lose any subsequent IPs (eg IP3 and IP4). To correct this, before an export I sort based on the number of IP properties - tada - the first object now has the most IPs in the array and hence none of the subsequent objects IPs are lost.
The downside is when you then have a second varying property - eg NICs. Once my sort is complete based on IP we then have the headings ServerName, IP1 - IP4 and NIC1. This means the subsequent object property of NIC2 is lost.
Is there a scalable way to ensure that you aren't losing data when exporting objects like this?

Answer 1

Try:
$o1 = New-Object psobject -Property #{
ServerName="Mordor"
IP1="10.0.0.1"
IP2="10.0.0.2"
NIC1="VMXNET"
NIC2="Broadcom"
}
$o2 = New-Object psobject -Property #{
ServerName="Rivendell"
IP1="10.1.1.1"
IP2="10.1.1.2"
IP3="10.1.1.3"
IP4="10.1.1.4"
NIC1="VMXNET"
}
$arr = #()
$arr += $o1
$arr += $o2
#Creating output
$prop = $arr | % { Get-Member -InputObject $_ -MemberType NoteProperty | Select -ExpandProperty Name } | Select -Unique | Sort-Object
$headers = #("ServerName")
$headers += $prop -notlike "ServerName"
$arr | ft -Property $headers
Output:
ServerName IP1 IP2 IP3 IP4 NIC1 NIC2
---------- --- --- --- --- ---- ----
Mordor 10.0.0.1 10.0.0.2 VMXNET Broadcom
Rivendell 10.1.1.1 10.1.1.2 10.1.1.3 10.1.1.4 VMXNET
If you know the types(NICS, IPS..), but not the count(ex. how many NICS) you could try:
#Creating output
$headers = $arr | % { Get-Member -InputObject $_ -MemberType NoteProperty | Select -ExpandProperty Name } | Select -Unique
$ipcount = ($headers -like "IP*").Count
$niccount = ($headers -like "NIC*").Count
$format = #("ServerName")
for ($i = 1; $i -le $ipcount; $i++) { $format += "IP$i" }
for ($i = 1; $i -le $niccount; $i++) { $format += "NIC$i" }
$arr | ft -Property $format

Answer 2

What about getting a list of all unique property headers and then doing a select on all the objects? When you do a select on an object for a nonexistent property it will create a blank one.
$allHeaders = $arrayOfObjects | % { Get-Member -inputobject $_ -membertype noteproperty | Select -expand Name } | Select -unique
$arrayOfObjects | Select $allHeaders
Granted you are looping through ever object to get the headers, so for a very large amount of objects it may take awhile.

Answer 3

Here's my attempt at a solution. I'm very tired now so hopefully it makes sense. Basically I'm calculating the largest amount of NIC and IP note properties, creating a place holder object that has those amounts of properties, adding it as the first item in a CSV, and then removing it from the CSV.
# Create example objects
$o1 = New-Object psobject -Property #{
ServerName="Mordor"
IP1="10.0.0.1"
IP2="10.0.0.2"
NIC1="VMXNET"
NIC2="Broadcom"
}
$o2 = New-Object psobject -Property #{
ServerName="Rivendell"
IP1="10.1.1.1"
IP2="10.1.1.2"
IP3="10.1.1.3"
IP4="10.1.1.4"
NIC1="VMXNET"
}
# Add to an array
$servers = #($o1, $o2)
# Calculate how many IP and NIC properties there are
$IPColSize = ($servers | Select IP* | %{($_ | gm -MemberType NoteProperty).Count} | Sort-Object -Descending)[0]
$NICColSize = ($servers | Select NIC* | %{($_ | gm -MemberType NoteProperty).Count} | Sort-Object -Descending)[0]
# Build a place holder object that will contain enough properties to cover all of the objects in the array.
$cmd = '$placeholder = "" | Select ServerName, {0}, {1}' -f (#(1..$IPColSize | %{"IP$_"}) -join ", "), (#(1..$NICColSize | %{"NIC$_"}) -join ", ")
Invoke-Expression $cmd
# Convert to CSV and remove the placeholder
$csv = $placeholder,$servers | %{$_ | Select *} | ConvertTo-Csv -NoTypeInformation
$csv | Select -First 1 -Last ($csv.Count-2) | ConvertFrom-Csv | Export-Csv Solution.csv -NoTypeInformation