Azure Function run code on startup

Question

I am trying to find a way to run some code one time (where I set connection strings, DI, and other configs) when my Azure function starts. So right now, it calls a Run method as the entrypoint with this in the generated function.json:

"entryPoint": "MyFunctionApp.MessageReceiver.Run"

This Run method uses an EventHubTrigger and processes incoming messages like so:

[FunctionName("MessageReceiver")]
        public static void Run([EventHubTrigger("eventHubName", Connection = "eventHubConnection")]string message, TraceWriter log)
        {
            if (string.IsNullOrWhiteSpace(message))
            {
                log.Info($"C# Event Hub trigger function processed a message: {message}");
            }
        }

Is there a way that I can run some code on the initial startup before this Run method is called? Or is there a way to declare an entrypoint that I can call before this class and then call Run() and somehow pass in the trigger? I am trying to find a way that avoids hackish stuff like setting boolean properties to see if the app has started.

Answer 1

You can implement an IExtensionConfigProvider. Those will be scanned and execute on "Startup".

using Microsoft.Azure.WebJobs.Host.Config;
namespace MyFunctionApp
{
  public class Startup : IExtensionConfigProvider
  {
     public void Initialize(ExtensionConfigContext context)
     {
        // Put your intialization code here.
     }
  }
}