ajkuma 13,366Reputation points• Microsoft Employee
Thanks for posting a good question.
To pass IWebAppsOperations into WebAppsOperationsExtensions.BackupAsync by invoking BackupAsync as an extension method of azure.WebApps.Inner. You could add extra NuGet packages. You can check Alex suggestions on your SO thread for more details.
You can also just re-post your question here to receive insights from the targeted audience.