Autofac

Question

我正在使用 Autofac。假设我有一个协变接口

interface IOptionFactory<out T> where T : IOption

和具体实现

class Option1Factory : IOptionFactory<Option1>
class Option2Factory : IOptionFactory<Option2>

我注册为

container.RegisterType<Option1Factory>.As<IOptionFactory<Option1>>();
container.RegisterType<Option2Factory>.As<IOptionFactory<Option2>>();

有没有办法解决IOptionFactory的所有实现？因为这是协变的，所以这在 C# 中应该是合法的（我说的对吗？）。类似于：

var factories = container.Resolve<IEnumerable<IOptionFactory<IOption>>>();

Answer 1

最好的解决方案是将您的代码包装在 Reporting class 中，其中 IEnumerable 属性 of IOptionFactory<IOption>.

private class Reporting
{
    private IEnumerable<IOptionFactory<IOption>> _allOptionsFactories;

    public Reporting(IEnumerable<IOptionFactory<IOption>> allOptionsFactories)
    {
        if (allOptionsFactories == null)
        {
            throw new ArgumentNullException("Parameter:" + nameof(allOptionsFactories));
        }
        this._allOptionsFactories = allOptionsFactories;
    }

    public void Report()
    {
        foreach (var optionsFactories in _allOptionsFactories)
        {
            Console.WriteLine(optionsFactories.GetType());
        }
    }
}

然后您可以注册并使用它们：

[TestMethod]
public void PassingParametersToRegister_NamedParameter()
{
    ContainerBuilder builder = new ContainerBuilder();

    builder.RegisterType<IOption1Factory1<SomeOption>>().As<IOptionFactory<IOption>>();
    builder.RegisterType<IOption1Factory2<SomeOption>>().As<IOptionFactory<IOption>>();
    builder.RegisterType<Reporting>();

    using (var container = builder.Build())
    {
        container.Resolve<Reporting>().Report();
    }

    //OUTPUT:

    //Enumerations + IOption1Factory1`1[Enumerations + SomeOption]
    //Enumerations + IOption1Factory2`1[Enumerations + SomeOption]
}

这是我 github

中的全部代码

Autofac - 解决不太具体的协变实现

Autofac - resolving less specific covariant implementations

c#

covariance