从控制台应用程序解析存储库时出现Microsoft Unity错误-NullReferenceException

Question

I'm having problems resolving a repository when calling it from a console app. Everything works fine when running the application (.NET 4, C#, Entity Framework, Unity) as normal, but I've created a standalone console app that will be run from the task scheduler to import feeds. I'm very close to giving up and do a dirty hack and write a script to call a webpage instead of using a console app, but I thought I'd at least try to understand why it isn't working first.

I'm new to both Entity Framework and Unity, so please bear with me and let me know if I've left out any important information.

This is the error I'm getting:

Resolution of the dependency failed, type = "MyNamespace.Domain.Template.IRepository`2[MyNamespace.Domain.Employees.OrganisationalUnit,System.Guid]", name = "(none)".
Exception occurred while: while resolving.
Exception is: NullReferenceException - Object reference not set to an instance of an object.

at Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable`1 resolverOverrides)
at Microsoft.Practices.Unity.UnityContainer.Resolve(Type t, String name, ResolverOverride[] resolverOverrides)
at Microsoft.Practices.Unity.UnityContainerExtensions.Resolve[T](IUnityContainer container, ResolverOverride[] overrides)
at MyNamespace.Infrastructure.FeedDefinition.GetOrganisationalUnit(String name, OrganisationalUnit parent) in C:\FeedDefinition.cs:line 552

This is the console app code:

static void Main(string[] args)
{
    if (args.Length > 0)
    {
        MyNamespace.Appliance.Configuration.Initialise.InitialiseContainer();

        ImportFeedProcessor importFeedProcessor = new ImportFeedProcessor();

        importFeedProcessor.Run(args[0]);
    }
}

And this is where it fails:

IRepository<OrganisationalUnit, Guid> organisationalUnitRepository = 
    Context.Instance.Container.Resolve<IRepository<OrganisationalUnit, Guid>>();

If anyone can help me understand what's going wrong I'd be very grateful!

UPDATE:

Here's the (important) bits from the initialise class:

public static void InitialiseContainer()
{
    UnityContainer container = new UnityContainer();

    // Use HttpContext for registering instances against for live
    IContext context = HttpContextWrapper.Instance;

    // Register the HttpContext as the default context to use
    container.RegisterInstance<IContext>(HttpContextWrapper.Instance);

    // repositories
    container.RegisterType<IRepository<Employee, Guid>, EmployeeRepository>(
        new UnityContextLifetimeManager(context),
                new InjectionConstructor(true, "OrganisationalUnit.Parent.Parent"));
    container.RegisterType<IRepository<OrganisationalUnit, Guid>, EntityFrameworkRepository<OrganisationalUnit, Guid>>(
                new UnityContextLifetimeManager(context),
                new InjectionConstructor("Parent.Parent"));

    // Create and populate a new Unity container from configuration
    Context.Instance.Container = container;
}

Is it perhaps the HttpContext that does it?

Thanks,

Annelie

Answer 1

One option you could consider is creating two different Initialise classes (I'm guessing that is your Unity bootstrapper class).

The one you have can be used for your web application.

The other one should be non-web specific. Remove any reference to HttpContext (it won't be available in a Console app) and UnityContextLifetimeManager (assuming this is HttpContext specific as well).