How to pass csv column object through function arg - powershell

Question

I have a lot of duplicate code I would like to clean up. I know the following syntax is not correct, but can you let me know the right way? Lets say I have the following code...
Function GetColumnOneValues
{
Param ($csvFile, $ValuesWithoutNullFile)
Import-Csv $csvFile | Where-Object {$_.test1ColumnOne} |
Export-Csv $ValuesWithoutNullFile -NoTypeInformation -Force
}
Function GetColumnTwoValues
{
Param ($csvFile, $ValuesWithoutNullFile)
Import-Csv $csvFile | Where-Object {$_.test2ColumnTwo} |
Export-Csv $ValuesWithoutNullFile -NoTypeInformation -Force
}
Function GetColumnThreeValues
{
Param ($csvFile, $ValuesWithoutNullFile)
Import-Csv $csvFile | Where-Object {$_.test3ColumnThree} |
Export-Csv $ValuesWithoutNullFile -NoTypeInformation -Force
}
^Notice the duplicate code
Function Main
{
$test1CsvFile = "C:\Scripts\Tests\test1.csv"
$test1CsvFileResults = "C:\Scripts\Tests\test1Results.csv"
$test2CsvFile = "C:\Scripts\Tests\test2.csv"
$test2CsvFileResults = "C:\Scripts\Tests\test2Results.csv"
$test3CsvFile = "C:\Scripts\Tests\test3.csv"
$test3CsvFileResults = "C:\Scripts\Tests\test3Results.csv"
GetColumnOneValues $test1CsvFile $test1CsvFileResults
GetColumnTwoValues $test2CsvFile $test2CsvFileResults
GetColumnThreeValues $test3CsvFile $test3CsvFileResults
}
Main
Instead, it should be something like this...
Function GetColumnValues
{
Param ($csvFile, $ValuesWithoutNullFile, $ColumnName)
Import-Csv $csvFile | Where-Object {$ColumnName} |
Export-Csv $ValuesWithoutNullFile -NoTypeInformation -Force
}
Function Main
{
$test1CsvFile = "C:\Scripts\Tests\test1.csv"
$test1CsvFileResults = "C:\Scripts\Tests\test1Results.csv"
$test2CsvFile = "C:\Scripts\Tests\test2.csv"
$test2CsvFileResults = "C:\Scripts\Tests\test2Results.csv"
$test3CsvFile = "C:\Scripts\Tests\test3.csv"
$test3CsvFileResults = "C:\Scripts\Tests\test3Results.csv"
$column1 = $_.test1ColumnOne
$column2 = $_.test2ColumnTwo
$column3 = $_.test3ColumnThree
GetColumnValues $test1CsvFile $test1CsvFileResults $column1
GetColumnValues $test2CsvFile $test2CsvFileResults $column2
GetColumnValues $test3CsvFile $test3CsvFileResults $column3
}
Main
However, instead of the function printing out the non-null value, it prints a blank csv file.
Use these csv Files to test the code...
csvFile1...
test1ColumnOne,test1ColumnTwo,test1ColumnThree
qwer,,
,qwer,
,,qwer
csvFile2...
test2ColumnOne,test2ColumnTwo,test2ColumnThree
asdf,,
,asdf,
,,asdf
csvFile3...
test3ColumnOne,test3ColumnTwo,test3ColumnThree
zxcv,,
,zxcv,
,,zxcv
Results should be...
test1Results.csv...
"test1ColumnOne","test1ColumnTwo","test1ColumnThree"
"qwer","",""
test2Results.csv...
"test2ColumnOne","test2ColumnTwo","test2ColumnThree"
"","asdf",""
test3Results.csv...
"test3ColumnOne","test3ColumnTwo","test3ColumnThree"
"","","zxcv"

Answer 1

If you want to clear empty values from a CSV column, retaining a list of non-empty values of that column, I'd do it with a generic function like this:
function Remove-EmptyValues {
Param(
[Parameter(
Mandatory=$true,
Position=0,
ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true
)]
[object[]]$Csv,
[Parameter(Mandatory=$true, Position=1)]
[string]$ColumnTitle
)
Process {
$Csv | Select-Object -Expand $ColumnTitle | Where-Object { $_ }
}
}
so it can be used like this
$csv = Import-Csv 'C:\testScripts\test.csv'
$noEmpty = Remove-EmptyValues $csv 'column A'
or like this:
$csv = Import-Csv 'C:\testScripts\test.csv'
$noEmpty = $csv | Remove-EmptyValues -ColumnTitle 'column A'
Edit: If you want to remove all lines where the value in a particular column is empty, pass input and output filename as well as the name of the column as string parameters:
function Remove-EmptyRecords {
Param(
[Parameter(Mandatory=$true, Position=0)]
[string]$Source,
[Parameter(Mandatory=$true, Position=1)]
[string]$Destination,
[Parameter(Mandatory=$true, Position=2)]
[string]$ColumnTitle
)
Import-Csv $Source |
Where-Object { $_.$ColumnTitle } |
Export-Csv $Destination -NoType
}
Remove-EmptyRecords test1.csv test1Results.csv test1ColumnOne
Remove-EmptyRecords test2.csv test2Results.csv test2ColumnTwo
Remove-EmptyRecords test3.csv test3Results.csv test3ColumnThree

Answer 2

Not sure exactly what you are getting at hear but you GetColumnValues so lets build a function with that goal. You have a columnName argument. Should add a -path one as well.
Function Get-ColumnValues{
Param ($Path, $ColumnName)
$csvData = Import-Csv $Path
If($ColumnName -in ($csvData | Get-Member -MemberType "NoteProperty").Name){
($csvData).$ColumnName | Where-Object{![string]::IsNullOrEmpty($_)}
} Else {
Throw "There is no column present called $ColumnName in the file $Path"
}
}
There is more error prevention that could be included here but simply put this will import a csv and return the values of the requested column assuming it exists.
As an aside the name of your function is misleading if you are exporting the results. You are not only getting them but setting them as well.