Assuming you refer to this flow: https://developers.google.com/accounts/docs/OAuth2ForDevices, it is not supported in the Google APIs Client Library for .NET. So you need to build it yourself though you may be able to reuse large parts of Google's stuff.
Notice that the "OAuth 2.0 flow for devices" is not a standardized OAuth 2.0 flow, so support is not ubiquitous. Also, the Google says elsewhere:
If your app will run on devices that do not have access to a system
browser, or devices with limited input capabilities (for example, if
your app will run on game consoles, video cameras, or printers), then
see Using OAuth 2.0 for Devices.
If that's really your use case you should pursue my suggestions, otherwise you should switch to https://developers.google.com/accounts/docs/OAuth2InstalledApp (see the flow chart on the right side there as well).