简单注入器注入 IEnumerable<Func<T>>

Question

如何使用 Simple Injector 注入 IEnumerable<Func<T>>？

只是为了添加一些上下文，我正在尝试创建所有知道如何处理一个特定事件的事件处理程序。这是我的 Container 注册：

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

这里有两个类实现了同一事件的 IHandleEvent<T> 接口：

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>>>();

我想收到IEnumerable<Func<IHandleDomainEvent<OrderConfirmed>>>

澄清一下，我知道如果我调用：

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

我会得到一个IEnumerable<IHandleDomainEvent<OrderConfirmed>>。

对于只有一种实现的接口，注册使用：

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

并在注册末尾添加如下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>>>();

Answer 1

这就是 Simple Injector 的优点：您永远不必解析 IEnumerable<Func<T>>，因为任何由 Simple Injector 解析的 IEnumerable<T> 已经作为 stream.

这意味着当您解析 IEnumerable<T> 时，流中的 none 元素将被解析。它们仅在迭代可枚举时得到解决，并得到解决 one-by-one.

迭代流时，元素将根据其生活方式进行解析。这意味着当集合中的元素 Transient 迭代流两次将导致创建新的瞬态实例。

示例：

// 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];

您可以在此处找到有关在 Simple Injector 中使用集合的更多信息：

简单注入器注入 IEnumerable<Func<T>>

Simple Injector Inject IEnumerable<Func<T>>

c#

dependency-injection

expression-trees

simple-injector