I am currently writing a bunch of triggers for an azure Webjob that need both ServiceBus endpoints and Queue Storage endpoints

Question

What I am trying to do is something along the lines of this :

public class BaseQueueTrigger
    {
        private readonly string _triggerNamee;
     
        public BaseQueueTrigger(string triggerNamee)
        {
            _triggerNamee = triggerNamee;
        }

        public void ProcessQueueMessage(
            [QueueTrigger("%" + _triggerNamee + "%")] string message)
        {
            ProcessMessage(message);
        }

        public void ProcessServiceBusMessage(
            [ServiceBusTrigger("%" + _triggerNamee + "%")] Message message)
        {
            ProcessMessage(Encoding.UTF8.GetString(message.Body));
        }

        protected virtual void ProcessMessage(string message)
        {
            Console.WriteLine($"Base class processing message: {message}");
        }
    }

What I would like is to have the child class send the queue name via the constructor to set up the endpoints and then have the individual processing of said endpoints happen in the child class once a trigger is hit.

The problem is that this requires a literal constant as the trigger name (compile time) and I am not sure if this approach is even possible.

Any help would be awesome :)

I tried creating a constant value in the child class and tried accessing it from the parent class via reflection but could not get it as a compile time constant value.

I have also considered to use the name of the child class as the queue trigger but will just be to impractical.

Answer 1

The %TriggerName% syntax is used in both the QueueTrigger and ServiceBusTrigger attributes. The value of TriggerName is passed to the constructor of the ChildQueueTrigger class, which in turn passes it to the constructor of the BaseQueueTrigger class.

When a message is received, the corresponding method in the child class is called, which in turn calls the corresponding method in the base class.

Code

public class BaseQueueTrigger
    {
        private readonly string _triggerName;

        public BaseQueueTrigger(string triggerName)
        {
            _triggerName = triggerName;
        }

        public void ProcessQueueMessage(
            [QueueTrigger("%TriggerName%")] string message)
        {
            ProcessMessage(message);
        }

        public void ProcessServiceBusMessage(
            [ServiceBusTrigger("%TriggerName%")] Message message)
        {
            ProcessMessage(Encoding.UTF8.GetString(message.Body));
        }

        protected virtual void ProcessMessage(string message)
        {
            Console.WriteLine($"Base class processing message: {message}");
        }
    }

    public class ChildQueueTrigger : BaseQueueTrigger
    {
        public ChildQueueTrigger(string triggerName) : base(triggerName)
        {
        }

        public void ProcessQueueMessage(
            [QueueTrigger("%TriggerName%")] string message)
        {
            Console.WriteLine($"Child class processing queue message: {message}");
            base.ProcessQueueMessage(message);
        }

        public void ProcessServiceBusMessage(
            [ServiceBusTrigger("%TriggerName%")] Message message)
        {
            Console.WriteLine($"Child class processing service bus message: {Encoding.UTF8.GetString(message.Body)}");
            base.ProcessServiceBusMessage(message);
        }
    }

Sample Output: