Add a way for an application to detect whether it's running inside the web client or not

Introduction

Add a way for an application to detect whether it's running inside the web client or not. I am not aware of any such possibility. For any terminal server session, there is the SystemInformation.TerminalServerSession property. It would be perfect if there could be a SystemInformation.TerminalServerWebclientSession. But any other way is also fine (e.g., a special environment variable).

Useful example

Instead of writing a file to the "normal" disk (inside the Azure VM), the application could write the file to the "Remote Desktop Virtual Drive"-Download folder. Now the file is truly on the user's local machine.