CODEWITHSUNDEEP
asp.net-web-api2autofacautofac-configuration
Sanjay Bathre
Sanjay Bathre

Reputation: 450

Autofac Null reference error web api 2

i am getting "An exception of type 'System.NullReferenceException' occurred in AutoFac Practice.dll but was not handled in user code" My code and configuration for Autofac is:

Autofac Configuration:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        var builder = new ContainerBuilder();

        // Register your Web API controllers.
        builder.RegisterApiControllers(Assembly.GetExecutingAssembly());

        // OPTIONAL: Register the Autofac filter provider.
        builder.RegisterWebApiFilterProvider(config);

        builder.RegisterType<SqlServerRepository>().As<IDBRepository>().InstancePerRequest();

        // Set the dependency resolver to be Autofac.
        var container = builder.Build();
        DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
        GlobalConfiguration.Configuration.DependencyResolver = new AutofacWebApiDependencyResolver(container);

        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

    }
}

Controller Code:

 public class HomeController : ApiController
{
    IDBRepository _repository;

    void Home(IDBRepository repository)
    {
        _repository = repository;
    }

    [HttpGet]
    public string Print()
    {
        return _repository.Print();
    }
}

Repository

interface IDBRepository
{
    //void Select();
    //void Insert();
    //void Update();
    //void Delete();

    string Print();
}

public class SqlServerRepository : IDBRepository
{
    public string Print()
    {
        return "hello there, i am Sql Server";
    }
}

In Controller i am getting error on this line: return _repository.Print(); saying object reference not set. _repository is not getting referenced i don't know what i am missing for the configuration.

Upvotes: 0

Views: 413

Answers (1)

fknx
fknx

Reputation: 1785

You must set the dependency (IDBRepository) in the controller's constructor.

So instead of this:

void Home(IDBRepository repository)
{
    _repository = repository;
}

you'll have to do:

public HomeController(IDBRepository repository)
{
    _repository = repository;
}

Upvotes: 1

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