Test for JSON member presence or absence.

I have code that creates a PSCustomObject via ConvertFrom-Json like:

    $jsonResponse = $webStreamReader.ReadToEnd() | ConvertFrom-Json

In some cases the JSON object will contain a field 'error' and other times it will contain a field named 'odata.error'. How do I test for the existence of these two fields in the PSCustomObject.

Thank you.

Kevin Burton