Unity IoC does not inject dependency into Web API Controller

Question

I\'m very new to using Unity, but my problem is that whenever I call my web service, I get an exception stating that

\"Make sure that the controller has a parameterl

Answer 1

• Install Unity.mvc5 and Unity.WebApi in a project through nuget package
• Specify fullnamespace as per below line

Example:

public static class UnityConfig
{
    public static void RegisterComponents()
    {
        var container = new UnityContainer();

        // register all your components with the container here
        // it is NOT necessary to register your controllers

        // e.g. container.RegisterType<ITestService, TestService>();

        DependencyResolver.SetResolver(new Unity.Mvc5.UnityDependencyResolver(container));

        GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);
    }
}

Answer 2

I know this is an old post but since I just ran into the same problem, the solution was to simply pass the config object to the Unity registration function and use the DependencyResolver from that instance:

EDIT: Just noted that the accepted answer does exacly this... Sorry for the spam ;-)

public static class UnityConfig
{
    public static void Register(HttpConfiguration config)
    {
        var container = new UnityContainer();

        // register your services here...

        // replace...
        /* GlobalConfiguration.Configuration.DependencyResolver = new      Unity.WebApi.UnityDependencyResolver(container); */

        // with this:
        config.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);
    }
}

Answer 3

Your Unity container is probably getting disposed because it's only defined in the scope of your WebApiConfig.Register() method. If you define your container as a member of Global, which will keep your container around for the lifetime of the app, it should work.

Edit: also don't forget to dispose the container on Application_End.

Answer 4

So, after hours of banging my head against a wall, I've found that this wasn't working because I had an OWIN/Katana Startup.cs class in my project. Now I don't know exactly what's going on here, so any more information would be great.

Basically, since I was using OWIN/Katana, I had a Startup.cs file that created a new HttpConfiguration object and configured it, similar to how it's done in the WebApiConfig.cs class.

private void ConfigureWebApi(HttpConfiguration config)
{
    config.MapHttpAttributeRoutes();
    var container = new UnityContainer();
    container.RegisterType<IValidator, Validator>();
    config.DependencyResolver = new UnityDependencyResolver(container);

    var jsonFormatter = config.Formatters.OfType<JsonMediaTypeFormatter().First();
    jsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
}

It looks like the code first runs through the WebApiConfig's Register function, and THEN overrides that HttpConfiguration object with the one generated in the Startup.cs file. I had to move my container setup stuff here in order for it to work.

Sorry that I didn't bring up the OWIN stuff before. This is fairly new to me and I didn't realize it was relevant. Hopefully this saves someone else the pain that I've just been through.