Content Comparison

// exceptions thrown outside of the while loop will cause messages to be errored. Exceptions within the while loop will cause a delayed retry.
public async Task ProcessMessagesAsync(IMessageBatchContext batch, CancellationToken cancellationToken)
{
      // your logic here...    

	  // while the channel/device is running, attempt to send the current batch (infinitely). Messages are
	  // never moved to the error queue.
      while (!cancellationToken.IsCancellationRequested)
      {
		try
		{
	      	var result = await SubmitToExternalService(someStream, cancellationToken).ConfigureAwait(false);
			// ... your code ...
			sendAttempt = 0;

			// ** you *must* mark your batch as processed **
	        batch.MarkBatchSuccessful();	// extension method in R11 and later
			// or
			batch.GetMessageContexts().ForEach(batchContext.MarkSuccessfullyProcessedForThisDevice);

            break;
		}
		catch(OperationCanceledException)
   	    {
	  		// exit when the device/channel is stopped
	        throw;
	    }
        catch(exception ex)
		{
        	// failure - retry
            var delay = TimeSpan.FromSeconds(10);
            if (sendAttempt > 3)
            	delay = TimeSpan.FromSeconds(60);
            else if (sendAttempt > 10)
            	delay = TimeSpan.FromMinutes(5);

			// this will record the exception in the event log (visible within the UI)
            Logger.Write(EventSeverity.Error, $"Failed to send batch to {someTarget}: {ex.Message}. Retry in {delay.TotalSeconds}s.");
            
			// wait before retrying
			await Task.Delay(delay, cancellationToken).ConfigureAwait(false);
            sendAttempt++;
        }
	}
}