Powershell create CSV files

I'm new to powershell. But learning.... I'm quite far with my script to achieve what i want. I just miss the last portion. I hope someone can The issue i have is don't get the correct result when creating an CSV file.

Ok, i have an CSV file something like this:

A           B
AAAA        111111
CCCC        222222
EEEE        333333
HHHH        444444

Now i have an array with this info:

AAAA
BBBB
CCCC
DDDD
HHHH

I compare the values in the array with the CSV file. And I want to receive the results of column B.

This is working fine. I receive this result:

111111
222222
444444

So basically this is correct. BUT.... I need to receive this:

So when the value is not found, I want an empty cell

I hope my question is clear enough ;)

The code i have is this:

$CSV = import-csv C:\tmp\mac-vendors-export.csv -Delimiter ';'
$vendormacarray = $Vendormac
$vendorname = foreach ($UniqueVendorMac in $Vendormacarray) {
    $csv | where-object {$_.A -match $UniqueVendorMac} | select-object  -Expand B
}

I think i have to add something like -or $_.A -eq 'null'.... but cannot figure this last part out.

Hopefully someone can help me out with this question.

Thank you

Solution

Use a hash table to store your items in A as its keys and the items in B as the values, that way you can perform fast lookups when comparing with $vendormacarray.

An example:

$map = @{}
Import-Csv C:\tmp\mac-vendors-export.csv -Delimiter ';' | ForEach-Object {
    $map[$_.A] = $_.B
}

$vendorMac = @(
    'AAAA'
    'BBBB'
    'CCCC'
    'DDDD'
    'HHHH'
)

$vendorMac | ForEach-Object {
    [pscustomobject]@{
        MAC      = $_
        ThingInB = $map[$_]
    }
}

Then the output using the data from your question would be something like:

MAC  ThingInB
---  --------
AAAA 111111
BBBB
CCCC 222222
DDDD
HHHH 444444