Instantiate empty csv variable - powershell

Question

I'm using methods to pick records from different csv files and I want to know how to create an empty variable that would act like a csv file. For Example...
an empty array would be $array = #()
an empty hash table would be $hashTable = #{}
a non-empty csv object would be $csvFileRecords = Import-Csv $someFileName
an empty csv object would be ????
What would the syntax be?

Answer 1

A "CSV object" is actually just an array (of psobjects).
$csvFileRecords = #()
To add new records to that array, you just need to add psobjects with appropriate attributes corresponding to the desired columns. One way to create a psobject with desired properties is from a hash table.
$obj = new-object psobject -property #{fname="Fiddle";lname="Freak"}
$csvFileRecords += $obj

Answer 2

Well, CSV's can't created from $null, but you could do something like this:
PS C:\> New-Object -TypeName System.Object | ConvertTo-Csv
#TYPE System.Object
But your challenge is that this doesn't work back and forth. For example:
PS U:\> ((New-Object -TypeName System.Int32 ) | ConvertTo-Csv).GetType()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True String System.Object
means that the output of ConvertTo-CSV is not null, but this shows where you've lost the pipeline:
PS U:\> ((New-Object -TypeName System.Int32 ) | ConvertTo-Csv | ConvertFrom-csv).GetType()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ ((New-Object -TypeName System.Int32 ) | ConvertTo-Csv | ConvertFrom-c ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
The help says:
Inputs
System.Management.Automation.PSObject
You can pipe any object that has an Extended Type System (ETS) adapter to ConvertTo-CSV.
So I bet your issue is that $null or blank doesn't have an ETS Adapter.
Here's some more reading on this: https://blogs.msdn.microsoft.com/besidethepoint/2011/11/22/psobject-and-the-adapted-and-extended-type-systems-ats-and-ets/