iocdependency injection issue when umbraco starts up - Extending Umbraco and using the API

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jake williamson 207 posts 873 karma points

Apr 18, 2018 @ 11:00

ioc/dependency injection issue when umbraco starts up

ok, i've been banging my head against the wall for far too long on this one and i just can't see how to make this work...

i'm using ninject for ioc and it's working using this code:

public class UmbracoBooter : IApplicationEventHandler
{
    public void OnApplicationInitialized(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
    }

    public void OnApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
    }

    public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        var kernel = new StandardKernel();

        kernel.Bind<IMyService>().To<MyService>();

        DependencyResolver.SetResolver(new NinjectDependencyResolver(kernel));
    }
}

i can inject 'IMyService' into a controller and it works e.g.

private readonly IMyService _myService;

public HomeController(IMyService myService)
{
    _myService = myService;
}

public override ActionResult Index(RenderModel model)
{
    _myService.DoSomething();

    return CurrentTemplate(model);
}

so far so good. however...

i actually want to call my 'DoSomething()' method when umbraco starts up (in the real project it's setting up a bunch of examine index stuff).

so the question is, how do i inject the 'IMyService' into my 'UmbracoBooter' class? if i try this:

private readonly IMyService _myService;

public Startup(IMyService myService)
{
    _myService = myService;
}

public void OnApplicationInitialized(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
{
}

public void OnApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
{
}

public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
{
    var kernel = new StandardKernel();

    kernel.Bind<IMyService>().To<MyService>();

    DependencyResolver.SetResolver(new NinjectDependencyResolver(kernel));

    _myService.DoSomething();
}

then '_myService' is always null...

i've tried everything i can think off and just can't get this to work... it feels like i need to inject and call the method further down the pipe maybe?

has anyone done this kinda thing before or am i attempting to do something that i shouldn't?!

any feedback would be blardy amazing ;)

cheers,

jake

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Euan Rae 105 posts 135 karma points

Apr 18, 2018 @ 11:59
1
Hi Jake,

You're correct; for this to work you need to create an instance of a class that takes an IMyService parameter in the constructor.

Is the code in _myService.DoSomething(); only ever done at application startup? If that's the case, then I would move it into the Bootstrapper class.

The way I handle startup code is to have a Bootstrapper class with a static function called Init, so the event handler looks something like
```
public void OnApplicationStarted(...)
{
    Bootstrapper.Init();
}
```
and Bootstrapper.Init() has all the code that's needed on application start; setting up IoC, creating custom database tables, setting up indexes, etc

Hope that helps!

Euan
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jake williamson 207 posts 873 karma points

Apr 18, 2018 @ 13:53
0
hi euan,

thank you so much for the reply, really appreciate it ;)

i see where you're going, moving the code in '_myService.DoSomething();' into the startup class would be ideal however (and you knew there'd be a however...) the implementation of the 'IMyService' interface (yup, you guessed it!) calls a method in another interface:
```
public class MyService : IMyService
{
    private readonly ILog _log;

    public MyService(ILog log)
    {
        _log = log;
    }

    public void DoSomething()
    {
        _log.Info(DateTime.Now);
    }
}
```
the trick being if i move this code into the startup i have to inject 'ILog' and i'm back to it being null... damn.

so i investigated the static class idea and i think i've got something working...

my startup class now has this:
```
public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
{
    var kernel = new StandardKernel();

    kernel.Bind<ILog>().ToMethod(context => LogManager.GetLogger(context.Request.Target.Member.DeclaringType));
    kernel.Bind<IMyService>().To<MyService>();

    DependencyResolver.SetResolver(new NinjectDependencyResolver(kernel));

    Bootstrapper.Init();
}
```
the bootstrapper has this:
```
public static class Bootstrapper
{
    private static IMyService MyService => DependencyResolver.Current.GetService<IMyService>();

    public static void Init()
    {
        MyService.DoSomething();
    }
}
```
based on the testing i've done, this is now working! i can't test my startup or boostrapper classes but tbh i couldnt really anyway and realistically there's no logic to test anyway... and it's the code in the implementation of 'IMyService' that has the testable code.

still got a bit of playing to do (like try this in a real project rather than the test project i'm using for this post) but does this sound about right?!

cheers,

jake
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Euan Rae 105 posts 135 karma points

Apr 19, 2018 @ 08:08
1
Hi Jake,

I think I see what your'e doing there, and what you're doing makes sense.

I would personally move the DI setup into another class / method, have another class that has an instance of IMyService in it and call them both from the OnApplication started event handler.
```
public void OnApplicationStarted (..)
{
    BootStrapper.Init(); // DI Setup Code goes in here
    StartupTasks.Run(); // (or whatever name suits based on what it's doing) instance of IMyService goes in here
}
```
This is just a personal preference in terms of separating out different pieces of functionality though.

I hope you get it working nicely in a live project!

Cheers, Euan
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