我知道有IServiceCollection
接口可以注册我的服务,IServiceProvider
可以实例化服务。使用ctor注入和ServiceProvider创建实例
如何基于指定类型实例化一个类,该类使用已注册的服务?
class MyClass
{
public MyClass(ISomeService someService) { }
}
var serviceCollection = new ServiceCollection();
serviceCollection.AddSingleton<ISomeService, SomeService>()
MyClass instance = CreateInstance(typeof(MyClass));
object CreateIntance(Type type)
{
???
}
例如,ASP.NET Core如何创建控制器实例?
我已经做了催化剂的幼稚执行,但在.NET核心中是不是有这样的东西?
private static object CreateInstance(Type type, IServiceProvider serviceProvider)
{
var ctor = type.GetConstructors()
.Where(c => c.IsPublic)
.OrderByDescending(c => c.GetParameters().Length)
.FirstOrDefault()
?? throw new InvalidOperationException($"No suitable contructor found on type '{type}'");
var injectionServices = ctor.GetParameters()
.Select(p => serviceProvider.GetRequiredService(p.ParameterType))
.ToArray();
return ctor.Invoke(injectionServices);
}
}
编辑:这是我的情景。我重构了一些实现此接口的遗留代码。
public interface IEventDispatcher
{
void RegisterHandler(Type handler);
void Dispatch(DomainEvent @event);
}
在调度方法实现我创建了处理程序实例:鉴于
public class MyClass {
public MyClass(ISomeService someService) {
//...
}
}
你需要建立整个对象图
public class InMemoryBus : IEventDispatcher
{
private readonly List<Type> _handlers = new List<Type>();
private readonly Func<Type, object> activator;
/// <param name="activator">Used to create instance of message handlers</param>
public InMemoryBus(Func<Type, object> activator)
{
this.activator = activator;
}
public void Dispatch(DomainEvent @event)
{
Type messageType = message.GetType();
var openInterface = typeof(IHandleMessages<>);
var closedInterface = openInterface.MakeGenericType(messageType);
var handlersToNotify = from h in _handlers
where closedInterface.GetTypeInfo().IsAssignableFrom(h.GetTypeInfo())
select h;
foreach (Type h in _handlersToNotify)
{
//this is the tricky part
var handlerInstance = activator(h);
closedInterface.GetTypeInfo()
.GetMethod(nameof(IHandleMessages<T>.Handle))
.Invoke(handlerInstance, new[] { message });
}
}
public void RegisterHandler(Type type) => _handlers.Add(type);
}
DI框架将为您做到这一点,只需将参数传递给您的构造函数。 – DavidG
serviceProvider.GetService()返回null。在CreateInstance(Type)方法中,我不知道编译时的参数是什么 –
Liero
然后我们可能需要查看一些如何注册所有服务的实际代码。 – DavidG