MEF 2 SatisfyImportsOnce 不适用于派生类型

Question

我很难理解为什么当我用接口的实现者而不是接口本身替换 ImportProperty 行时我的代码能正常工作：

[TestFixture]
public class FlyweightTest
{
    [MetadataAttribute]
    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
    class FlyweightIntegerKeyAttribute : ExportAttribute, IFlyweightKey<int>
    {
        public int Key { get; private set; }

        public FlyweightIntegerKeyAttribute(int key) : base(typeof(IAbstraction)) { Key = key; }
    }

    public interface IAbstraction { }

    [FlyweightIntegerKey(1)]
    class Abstraction1 : IAbstraction { }

    [FlyweightIntegerKey(2)]
    class Abstraction2 : IAbstraction { }

    [Test]
    public void Test()
    {
        IMefFlyweight<IAbstraction, IFlyweightKey<int>> lFlyweight = new Flyweight();

        Initialize(lFlyweight);

        Assert.AreEqual(2, lFlyweight.Abstractions.Count());
        Assert.IsTrue(lFlyweight.Abstractions.Select(lazy => lazy.Value).OfType<Abstraction1>().Any());
        Assert.IsTrue(lFlyweight.Abstractions.Select(lazy => lazy.Value).OfType<Abstraction2>().Any());
    }

    //public interface IMefFlyweight<T, TMetadata>
    //{
    //    IEnumerable<Lazy<T, TMetadata>> Abstractions { get; set; }
    //}

    public class Flyweight : IMefFlyweight<IAbstraction, IFlyweightKey<int>>
    {
        public IEnumerable<Lazy<IAbstraction, IFlyweightKey<int>>> Abstractions { get; set; }
    }

    public void Initialize(IMefFlyweight<IAbstraction, IFlyweightKey<int>> @object)
    {
        var catalog = new AggregateCatalog();
        var registrationBuilder = new RegistrationBuilder();

        registrationBuilder.ForTypesDerivedFrom<IAbstraction>().Export<Lazy<IAbstraction, IFlyweightKey<int>>>();

        //registrationBuilder.ForTypesDerivedFrom<IMefFlyweight<IAbstraction, IFlyweightKey<int>>>().ImportProperty(flyweight => flyweight.Abstractions);
        // This one works:
        registrationBuilder.ForType<Flyweight>().ImportProperty(flyweight => flyweight.Abstractions);

        foreach (var lAssembly in AppDomain.CurrentDomain.GetAssemblies())
            catalog.Catalogs.Add(new AssemblyCatalog(lAssembly, registrationBuilder));

        var container = new CompositionContainer(catalog);

        container.SatisfyImportsOnce(@object, registrationBuilder);
    }

那个：

registrationBuilder.ForType().ImportProperty(flyweight => flyweight.Abstractions)

工作正常但是：

registrationBuilder.ForTypesDerivedFrom>>().ImportProperty(flyweight => flyweight.Abstractions)

虽然我认为它们在我的情况下应该是等效的。

Answer 1

我意识到 "import" 只适用于类而不是接口。

解决方案可能是导入所有属性：

registrationBuilder.ForTypesDerivedFrom<IImportingInterface>().ImportProperties(_ => true);

或

registrationBuilder.ForTypesDerivedFrom<IImportingInterface>().ImportProperties<ExportClass>(_ => true);

MEF 2 SatisfyImportsOnce 不适用于派生类型

MEF 2 SatisfyImportsOnce does not work on derived types

c#

mef