Problem with exporting and appending data to csv file - powershell

Question

The situation is the following - I've got a csv file with number of columns (let's say 3) and custom object with same columns but one will be a new one. I want to compare column names and if there is a new one, then add column and then add values accordingly to csv file and I don't want to replace all existing content in current csv file. Here is the code I've written, but I'm getting error: The appended object does not have a property that c
orresponds to the following column: column1. To continue with mismatched properties, add the -Force parameter, and then retry the command.
File sample:
Output should be same file, but with new column 'column4' and new row containing, like this:
I can't figure out what I'm doing wrong.
$file_path = '..path_to_the_file\test_csv.csv'
$csv = import-csv -path $file_path
$columns = #([pscustomobject]#{
column1 = 'something_new_1'
column2 = 'something_new_2'
column3 = 'something_new_3'
column4 = 'something_new_4'
}
)
$csv_columns = ($csv | get-member).where({$_.Membertype -eq 'NoteProperty'}).Name
$columns = ($columns | get-member).where({$_.Membertype -eq 'NoteProperty'}).Name
$compare = $columns | Where-Object {$csv_columns -notContains $_}
foreach ($column in $csv) {
$column | add-member -MemberType NoteProperty -Name $compare -value ''
}
$csv | export-csv -Path $file_path -NoTypeInformation
$columns | export-csv -path $file_path -Append -NoTypeInformation -force

Answer 1

You can use this function to streamline the process, this of course assumes the objects you want to append already has the same properties as the ones in the array of objects and will only add new ones.
function Add-ObjectNormalized {
[CmdletBinding()]
param(
[Parameter(Mandatory, ValueFromPipeline)]
[object] $InputObject,
[Parameter(Mandatory, Position = 0)]
[object[]] $AddObject
)
begin {
$isFirstObject = $false
$propertiesToAdd = [Collections.Generic.HashSet[string]]::new(
[string[]] $AddObject[0].PSObject.Properties.Name,
[System.StringComparer]::OrdinalIgnoreCase
)
}
process {
if(-not $isFirstObject) {
$isFirstObject = $true
$propertiesToAdd.ExceptWith([string[]] $InputObject.PSObject.Properties.Name)
}
$psobject = $InputObject.PSObject.Properties
foreach($prop in $propertiesToAdd) {
$psobject.Add([psnoteproperty]::new($prop, $null))
}
$InputObject
}
end {
$AddObject
}
}
Pipe it after Import-Csv including the array of objects to be added as argument. For example:
$objects = #(
[pscustomobject]#{
column1 = 'something_new_1'
column2 = 'something_new_2'
column3 = 'something_new_3'
column4 = 'something_new_4'
}
[pscustomobject]#{
column1 = 'something_new_5'
column2 = 'something_new_6'
column3 = 'something_new_7'
column4 = 'something_new_8'
}
)
Import-Csv path\to\csv.csv | Add-ObjectNormalized $objects |
Export-Csv path\to\newCsv.csv -NoTypeInformation
The output using a simple Csv like the one in question would be:
column1 column2 column3 column4
------- ------- ------- -------
va1 val2 val3
something_new_1 something_new_2 something_new_3 something_new_4
something_new_5 something_new_6 something_new_7 something_new_8