Don't quite understand powershells "-Join" and "ConvertTo-Csv" - powershell

Question

I have this code to create a csv and display it as a table:
$Keys = ("OrderDate","Region","Rep","Product","Units","Unit Cost","Total")
$Csv = #()
$Keys | ForEach-Object {
$Csv += $_ -Join ","
}
$Csv | ConvertFrom-Csv
My output is:
OrderDate
OrderDate,Region
OrderDate,Region,Rep
OrderDate,Region,Rep,Product
OrderDate,Region,Rep,Product,Units
OrderDate,Region,Rep,Product,Units,Unit Cost
OrderDate,Region,Rep,Product,Units,Unit Cost,Total
OrderDate
---------
Region
Rep
Product
Units
Unit Cost
Total
I would like these lines to be formatted as headers of a table, like this:
OrderDate Region Rep ProductUnits Unit Cost Total
----------- -------- ---- --------------- ----------- ------

Answer 1

What you're attempting can be done like this:
$Keys = "OrderDate","Region","Rep","Product","Units","Unit Cost","Total"
$Object = Select-Object -InputObject 0 -Property $Keys
That's typically most useful when you don't know what the properties are when writing the script. The input object doesn't matter as long as it's a scalar value (i.e., not a collection).
To get the exact output you've specified, you'd have to do $Object | Format-Table because PowerShell defaults to list output for custom objects, but that changes the object into a string so it's just for display.
A more generally useful pattern to create an object when you do know the properties is to do this:
$Object = [PSCustomObject]#{
"OrderDate" = # Some Value
"Region" = # Some Value
"Rep" = # Some Value
"Product" = # Some Value
"Units" = # Some Value
"Unit Cost" = # Some Value
"Total" = # Some Value
}
Here you instance the object and assign the values you want immediately.