How to perform dependency injection using Azure WebJobs SDK

Question

The problem is that the Azure WebJobs SDK supports only public static methods as job entry-points which means there is no way of implementing constructor/property injection.

I am unable to find anything about this topic in official WebJobs SDK documentation/resources. The only solution that I came across is based on service locator (anti) pattern described on this post here.

Is there a good way to use "proper" dependency injection for projects based on Azure WebJobs SDK?

Answer 1

Azure WebJobs SDK now supports instance methods. Combining this with a custom IJobActivator allows you to use DI.

First, create the custom IJobActivator that can resolve a job type using your favourite DI container:

public class MyActivator : IJobActivator
{
    private readonly IUnityContainer _container;

    public MyActivator(IUnityContainer container)
    {
        _container = container;
    }

    public T CreateInstance<T>()
    {
        return _container.Resolve<T>();
    }
}

You need to register this class using a custom JobHostConfiguration:

var config = new JobHostConfiguration
{
    JobActivator = new MyActivator(myContainer)
};
var host = new JobHost(config);

Then, you can use a simple class with instance methods for your jobs (here I'm using Unity's constructor injection feature):

public class MyFunctions
{
    private readonly ISomeDependency _dependency;

    public MyFunctions(ISomeDependency dependency)
    {
        _dependency = dependency;
    }

    public Task DoStuffAsync([QueueTrigger("queue")] string message)
    {
        Console.WriteLine("Injected dependency: {0}", _dependency);

        return Task.FromResult(true);
    }
}

Hope it helped!