You need to watch for Transient errors if you use SQL Server in Azure. Transient errors or Retriable errors can occur any time and your application should be smart enough to retry these failed operations. Azure might quickly shift hardware resources of your database to give you a better load-balance, when this happens your application might not be able to connect to the database. Since these reconfiguration events completes quickly, your application needs to be designed to handle these faults.This adds more complexity to your code because you need to write code to handle this manually.
Preview version of Microsoft.Data.SqlClient library now supports RetryLogic function, you do not need to write any manual code to handle Transient or retriable errors anymore.
Click through for more details as well as a demonstration. I’m surprised it took this long, to be honest—useful retry logic is exactly the type of thing which should be in the bowels of a library rather than littered throughout business code (or worse, not even in business code).