In PowerShell 7.4.5, I ran into a weird issue with Where-Object a.k.a. ?.

Let’s assume $players is System.Collections.Generic.List and contains for example these objects that I get from Invoke-RestMethod:

Id          : 536069
User_id     : 2739325
Elo1v1      : 1511
Elo2v2Solo  : 1907
Elo2v2Team  : 2222
TeamIndex   : 0
PlayerIndex : 2

Id          : 278305
User_id     : 1735386
Elo1v1      : 1443
Elo2v2Solo  : 1788
Elo2v2Team  : 1279
TeamIndex   : 1
PlayerIndex : 1

and $myUserId is 1735386.

I then tried to run:

$myself = $players | ? User_id -eq $myUserId | Select -First 1

but it caused a lot of chaos and debugging as it worked under some scenarios when my further code was different, then consistently stopped working completely – $myself was empty.

After bunch of tries, I changed it to:

$myself = $players | ? { $_.User_id -eq $myUserId } | Select -First 1

and it started working consistently.

Why? What’s wrong with the first version? I would assume something related to the underscore in the property name, but then this works fine and always returns an object:

$opponent = $players | ? User_id -ne $myUserId | Select -First 1

I couldn’t find anything about underscore or similar characters in docs.