Array in a foreach loop - powershell

Question

What am I doing wrong here?
The mailbox has an active an inactive mailbox so it will return two mailboxes.
However, when trying to capture the output, I am only getting the last account in the array
Note, this is a simplified version of a larger script, but kept it simple for this example.
$guid = import-csv "c:\temp\Mailboxes.csv"
$DAta = New-Object psobject
$Data | Add-Member -MemberType NoteProperty -Name alias -Value $null
$Data | Add-Member -MemberType NoteProperty -Name guid -Value $null
$mbxcol = #()
#$data = $null
foreach ($G in $Guid){
$mbx = Get-mailbox $g.alias -IncludeInactiveMailbox
$data.alias = $mbx.alias
$data.guid = $mbx.guid
$MBXCol += $Data
}
$mbxcol

Answer 1

As explained in comments, every array element is a reference of the same object ($Data), a simple way to demonstrate using Object.ReferenceEquals Mehod with this example:
foreach ($item in 0..10) {
$data.Alias = 'mailbox{0}' -f $item
$data.Guid = [guid]::NewGuid()
$mbxcol += $data
}
[object]::ReferenceEquals($data, $mbxcol[0]) # -> True
As for how to simplify and make your code more efficient, do not add elements (+=) to a fixed collection (#( )):
$result = (Import-Csv "c:\temp\Mailboxes.csv").Alias |
Get-Mailbox -IncludeInactiveMailbox |
Select-Object Alias, Guid

Answer 2

A much more simple example of your code is:
$guid = ("A","B")
$Data = New-Object psobject
$Data | Add-Member -MemberType NoteProperty -Name alias -Value $null
$mbxcol = #()
foreach ($G in $Guid){
$mbx = $g
$data.alias = $mbx
$MBXCol += $Data
}
$mbxcol
As #Santiago mentioned in his comment, $Data is a reference to an object, so each time you update it, you overwrite it, even if it is in an array. To fix this, instantiate the object each loop as follows:
$guid = ("A","B")
$mbxcol = #()
foreach ($G in $Guid){
$Data = New-Object psobject
$Data | Add-Member -MemberType NoteProperty -Name alias -Value $null
$mbx = $g
$data.alias = $mbx
$MBXCol += $Data
}
$mbxcol