Handle failures at the right boundary

The idea

PowerShell distinguishes terminating errors, which interrupt the current operation, from nonterminating errors that may allow processing to continue. Try and catch handle terminating errors. When a cmdlet operation must succeed, -ErrorAction Stop can promote its nonterminating error into one that catch handles. Keep the protected block narrow enough that its recovery policy matches the operations it contains.

Finally provides a cleanup path whether the protected work succeeds or fails. Do not claim success after catching an error unless recovery actually completed. Native programs have exit codes whose interpretation follows that program’s contract; inspect $LASTEXITCODE promptly rather than assuming cmdlet error behavior applies identically. Preserve data and diagnostic channels so callers can distinguish partial output from a fully successful operation.

try {
  Write-Error "Invalid sample" -ErrorAction Stop
  "unreachable"
} catch {
  "handled"
} finally {
  "cleanup"
}

handled
cleanup

ErrorAction Stop makes this error terminating. Catch handles it, the remaining try statement is skipped, and finally still executes.