title: Custom SQL filter in Azure Service Bus Topic Subscription
body: <p>I am working on an Azure function app that gets triggered when there is a new message in the dead-letter-queue of a topic's subscription. This FA is meant only to read the message from DLQ and not process it (not calling .Complete()). The issue here is that every time when there is a new message in DLQ, the FA gets triggered for all the previous messages as well. This makes the FA running continuously.</p>
  <p>I was thinking of implementing a subscription filter wherein I can put a custom C# like logic.
  Basically, I want to trigger the FA only if the message is new ie the message's sys.EnqueuedTimeUtc is no older than 30 sec from now.</p>
  <p>Can anyone please suggest me the filter code for above logic ?</p>