According to documentation:
https://cloud.google.com/storage/docs/configuring-cors#code-samples
Currently, there is no possibility to set CORS using c# client library.
"For more information, see the Cloud Storage C# API reference documentation.
You cannot currently configure CORS with the C# client library."
Can you implement in new nuget for c# client library possibility to set CORS? Could you at least put this item to your backlog?