简单注入器：注入IEnumerable<Func<T>>

Question

简单注入器：注入IEnumerable<Func<T>>

c#dependency-injectionexpression-treessimple-injector

3

我如何使用 Simple Injector 注入 IEnumerable>？

简要介绍一下，我正试图创建所有 EventHandlers ，这些处理程序知道如何处理一个特定的事件。这是我的容器注册代码：

container.RegisterCollection(typeof(IHandleDomainEvent<>),
    AppDomain.CurrentDomain.GetAssemblies());

以下是两个实现相同事件的 IHandleEvent<T> 接口的类：

public class Reservation : IHandleDomainEvent<OrderConfirmed>{}
public class Order: IHandleDomainEvent<OrderConfirmed>{}

所以当我调用Simple Injector时：

var handlers = _container.GetAllInstances<Func<IHandleDomainEvent<OrderConfirmed>>>();

我希望能够收到 IEnumerable<Func<IHandleDomainEvent<OrderConfirmed>>>

只是为了澄清，我知道如果我调用：

var handlers = _container.GetAllInstances<IHandleDomainEvent<OrderConfirmed>>();

我会得到一个 `IEnumerable>`。

对于只有一个实现的接口，可以使用以下方式进行注册：

container.Register(typeof(IHandleDomainEvent<>),
    AppDomain.CurrentDomain.GetAssemblies(), Lifestyle.Scoped);

在注册的末尾添加以下ResolveUnregisteredType：

container.ResolveUnregisteredType += (o, args) => ResolveFuncOfT(o, args, container);

// Function
private static void ResolveFuncOfT(object s, UnregisteredTypeEventArgs e, Container container)
{
    var type = e.UnregisteredServiceType;
    if (!type.IsGenericType || type.GetGenericTypeDefinition() != typeof(Func<>)) return;
    Type serviceType = type.GetGenericArguments().First();
    InstanceProducer producer = container.GetRegistration(serviceType, true);
    Type funcType = typeof(Func<>).MakeGenericType(serviceType);
    var factoryDelegate = Expression.Lambda(funcType, producer.BuildExpression()).Compile();
    e.Register(Expression.Constant(factoryDelegate));
}

将允许调用：

var handler = _container.GetInstance<Func<IHandleDomainEvent<TEvent>>>();

- Rodrigo Riskalla Leal

1个回答

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- Steven · Accepted Answer

这就是Simple Injector的优美之处：您永远不必解析IEnumerable<Func<T>>，因为由Simple Injector解析的任何IEnumerable<T>都已经作为一个流运行。

这意味着当您解析IEnumerable<T>时，流中的元素都不会被解析。只有在枚举流时才会逐个解析。

在枚举流时，元素将根据其生命周期进行解析。这意味着当集合中的元素是Transient时，两次枚举流将导致创建新的瞬态实例。

例如：

// Only resolves the enumerable, not the contained handlers.
// This enumerable itself is a singleton, you can reference it forever.
var collection = container.GetInstances<IEventHandler<OrderConfirmed>>();

// Calls back into the container to get the first element, but nothing more
var first = collection.First();

// Since the stream that Simple Injector returns is a IList<T>, getting the last
// element is an O(1) operation, meaning that only the last element is resolved;
// not the complete collection.
var last = collection.Last();

// Calling .ToArray(), however, will obviously resolve all registrations that are 
// part of the collection.
var all = collection.ToArray();

// Iterating a stream will always call back into the container, which ensures
// that the stream adheres to the elements lifestyles. Transients will be
// created on each iteration, while singletons will only be created once.
container.Register<Apple>(Lifestyle.Transient);
container.Register<Banana>(Lifestyle.Singleton);
container.RegisterCollection<IFruit>(typeof(Apple), typeof(Banana));
var fruits = container.GetAllInstances<IFruit>();
Assert.AreNotSame(fruits.First(), fruits.First());
Assert.AreSame(fruits.Last(), fruits.Last());

// Even other collection types such as IReadOnlyCollection<T> behave as streams
var col = container.GetInstance<IReadOnlyCollection<IEventHandler<OrderConfirmed>>();

// This gives you the possibility to get a particular item by its index.
var indexedItem = col[3];

您可以在 Simple Injector 的这里找到有关处理集合的更多信息：