-contains or -match several values - powershell

Question

I have to filter my results by certain strings and tried to do it with -match and -contains.
-match works if I have just one value to filter, but not with an array.
-contains neither works with one string, nor with a string array.
Why isn't it working with several values? Especially the -contains. Or is there another easy way to solve it?
$Folder = 'C:\Test'
$filterArray = #('2017-05', '2017-08')
$filter = '2017-05'
## test with -MATCH
## working with one match string
Get-ChildItem -Path $Folder -Recurse -Include *.txt |
Where { $_.FullName -match $filter } |
ForEach-Object { $_.FullName }
## NOT working with match string array - no results
Get-ChildItem -Path $Folder -Recurse -Include *.txt |
Where { $_.FullName -match $filterArray } |
ForEach-Object { $_.FullName }
## test with -CONTAINS
## NOT working with one contains string - no results
Get-ChildItem -Path $Folder -Recurse -Include *.txt |
Where { $_.FullName -contains $filter } |
ForEach-Object { $_.FullName }
## NOT working with contains string array- no results
Get-ChildItem -Path $Folder -Recurse -Include *.txt |
Where { $_.FullName -contains $filterArray } |
ForEach-Object { $_.FullName }

Answer 1

Using an array as the second operand for the -match or -contains operators doesn't work. There are basically two approaches you could take:
Build a regular expression from the array and use that with the -match operator:
$pattern = #($filterArray | ForEach-Object {[regex]::Escape($_)}) -join '|'
... | Where-Object { $_.FullName -match $pattern }
This is the preferred approach.
Use a nested Where-Object filter and the String.Contains() method:
... | Where-Object {
$f = $_.FullName
$filterArray | Where-Object { $f.Contains($_) }
}

Answer 2

Why isn't it working with several values?
Because these operators were designed to test against a single argument, plain and simple.
The ability to match against multiple arguments in a single operation would beg the question: "Does the input need to satisfy all or any of the argument conditions"?
If you want to test for a match against any of an array of regex patterns, you can construct a single pattern from them using a non-capturing group, like so:
$filterPattern = '(?:{0})' -f ($filterArray -join '|')
Get-ChildItem -Path $Folder -Recurse -Include *.txt | Where {$_.FullName -match $filterPattern} | ForEach-Object{ $_.FullName }
You can also drop the Where-Object and ForEach-Object loop completely, since PowerShell 3.0 supports property enumeration:
(Get-ChildItem -Path $Folder -Recurse -Include *.txt).FullName -match $filterPattern