using Add-Member to create object from an array

Question

I am using a script to create new objects with certain values given as below. This works in cases where $Names returns a single string value, however get’s the following error when there is an array and before printing $newobj. Trying to find what is causing the error as I added a foreach statement for $Names. Also note that, the value of $x is same as "London" for both values John, Jake in the $names array.

In the current output, StudentName is printed as “John” both times, and when I use parameter –Force, the value of StudentName is “Jake" both times. I would need to separate these values different in the output. Could someone help me please?

Add-Member : Cannot add a member with the name "StudentName" because a member with that name already exists. To overwrite the
member anyway, add the Force parameter to your command.
At E:\test.ps1:93 char:14
+             $newobj | Add-Member -MemberType NoteProperty -Name StudentName -Value $_

Script:

# $DCNames is an array

Foreach($x in $DCNames){
        $newobj = New-Object psobject
        $newobj | Add-Member -MemberType NoteProperty -Name DC -Value $x

        ######  $Names in most cases is a single string or it could be also an array. For example: it could be a value Adam or {John Jake….} and so I would need to Add each member in $Names as StudentName object below.
        $Names =@()
        $Names = $List | Where-Object{$_.Name -eq $x} | Select -ExpandProperty Name

        $Names | foreach {
            $newobj | Add-Member -MemberType NoteProperty -Name StudentName -Value $_   
            # $ClassName is a single string
            $newobj | Add-Member -MemberType NoteProperty -Name Class -Value $ClassName
            $newobj
            }

Current output:

Name: Vegas
StudentName: Adam
Class: 10

Name: London
StudentName: John
Class: 12

Name: London
StudentName: John (the script should take the second value “Jake” here from $Names array, but is not happening for some reason)
Class: 11

Just add it as a whole, be it an array or single value, don't enumerate it. I don't see any other options. — woxxom
– woxxom, Commented Aug 31, 2016 at 8:21
when i export $newobj to a CSV, i see System.Object[] for the same and can't read the actual values. How should i convert that to a readable array object? — user3331975
– user3331975, Commented Aug 31, 2016 at 8:50
Ah! CSV changes the deal. So you want to keep all names in one column cell which means you have to -join them in one string separated by a semicolon for example. — woxxom
– woxxom, Commented Aug 31, 2016 at 9:03

Mathias R. Jessen · Accepted Answer · 2016-08-31 12:30:05Z

1

You create only 1 object, and attempt to overwrite the StudentName on that same object. Do it like this instead:

Foreach($x in $DCNames){
    ######  $Names in most cases is a single string or it could be also an array. For example: it could be a value Adam or {John Jake….} and so I would need to Add each member in $Names as StudentName object below.
    $Names = @()
    $Names = $List | Where-Object{$_.Name -eq $x} | Select -ExpandProperty Name

    $Names | foreach {
        $newobj = New-Object psobject
        $newobj | Add-Member -MemberType NoteProperty -Name DC -Value $x
        $newobj | Add-Member -MemberType NoteProperty -Name StudentName -Value $_ 
        $newobj | Add-Member -MemberType NoteProperty -Name Class -Value $ClassName
        $newobj
    }
}

Piping to Add-Member can be quite slow, you may want to use New-Object -Property @{} instead:

Foreach($x in $DCNames){
    ######  $Names in most cases is a single string or it could be also an array. For example: it could be a value Adam or {John Jake….} and so I would need to Add each member in $Names as StudentName object below.
    $Names = @()
    $Names = $List | Where-Object{$_.Name -eq $x} | Select -ExpandProperty Name

    $Names | foreach {
        $newobj = New-Object psobject -Property @{
            DC = $x
            StudentName = $_ 
            Class = $ClassName
        }
    }
}

answered Aug 31, 2016 at 12:30

Mathias R. Jessen

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2 Comments

user3331975 Over a year ago

Thanks much Mathias. The first example worked.. Regarding New-Object example, I would need to run few cmdlets and get other values based on $x, $Names , $_ and after the New-Object step. In this case, how should we add those new ones into $newobj?

Mathias R. Jessen Over a year ago

@user3331975 create a bunch of hashtables to hold the data, then at the very end, create the objects based on these hashtables :)

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