CODEWITHSUNDEEP
dependency-injectionninject
Mark Feldman
Mark Feldman

Reputation: 16119

Ninject injecting wrong type

I have a class with a property of type ICollection<object> that I'm trying to inject with an instance of type ObservableCollection<object>. If I obtain an instance via Get<> Ninject gives me the correct type, but if I get it to inject it into a class it creates a List<object> instead. Can anyone explain to me what's going on?

using Ninject;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;

namespace NinjectTest
{
    class Program
    {
        static void Main(string[] args)
        {
            IKernel kernel = new StandardKernel();
            kernel.Bind<MyClass>().ToSelf();
            kernel.Bind<ICollection<object>>().To(typeof(ObservableCollection<object>));

            ICollection<object> foo = kernel.Get<ICollection<object>>();
            ICollection<object> bar = kernel.Get<MyClass>().Collection;

            Debug.Assert(foo is ObservableCollection<object>); // ok
            Debug.Assert(bar is ObservableCollection<object>); // fails
        }
    }

    public class MyClass
    {
        [Inject] public ICollection<object> Collection { get; set; }
    }
}

Upvotes: 0

Views: 62

Answers (1)

BatteryBackupUnit
BatteryBackupUnit

Reputation: 13233

This is per the "Multi Injection" feature. When you try to inject an array [], an IEnumerable<T>, an ICollection<T> or an IList<T> it is always interpreted as GetAll<T> - so it will create an instance of each binding for T and return it as the "collection" type you've requested.

So far what i've done is create specific interfaces like:

public interface IFooCollection : ICollection<Foo>

and then ctor-inject an IFooCollection. This way you work around the multi injection feature. Of course you could also create an interface for the observable collection:

public interface IObservableCollection<T> : ICollection<T>, INotifyCollectionChanged

Upvotes: 2

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