注册'半封闭'通用组件 [英] Registering 'half-closed' generic component

问题描述

我有两个接口：

  public interface IQuery< TResult> {} 
 
 public interface IQueryHandler< in TQuery，out TResult> 
其中TQuery：IQuery< TResult> 
 {
 TResult Handle（TQuery q）; 
} 
  

一个关闭IQueryHandler实现的例子：

  public class EventBookingsHandler：IQueryHandler< EventBookings，IEnumerable< EventBooking>> 
 {
 private readonly DbContext _context; 
 
 public EventBookingsHandler（DbContext context）
 {
 _context = context; 
} 
 
 public IEnumerable< EventBooking> Handle（EventBookings q）
 {
 return _context.Set< MemberEvent>（）
 .OfEvent（q.EventId）
 .AsEnumerable（）
 .Select（EventBooking .FromMemberEvent）; 
 
 
 $ / code> 

我可以注册和解析<$



  Classes.FromAssemblyContaining（typeof> c $ c $> IQueryHandler<，>  （IQueryHandler<，>））
 .BasedOn（typeof（IQueryHandler<，>））
 .WithServiceAllInterfaces（）
  

然而，我想要做的是解决一个半关闭的开放式泛型实现（即指定一个通用的 TQuery 类型参数）：

  public class GetById< TEntity> ：IQuery< TEntity>其中TEntity：class，IIdentity 
 {
 public int Id {get;私人设置; } 
 
 public GetById（int id）
 {
 Id = id; 
} 
} 
 
 public class GetByIdHandler< TEntity> ：IQueryHandler< GetById< TEntity>，TEntity>其中TEntity：class，IIdentity 
 {
 private readonly DbContext _context; 
 
 public GetByIdHandler（DbContext context）
 {
 _context = context; 
 
 
 public TEntity Handle（GetById< TEntity> q）
 {
 return _context.Set< TEntity>（）。Find（q.Id）; 
 
 
  

当我试图解析 IqueryHandler< GetById< Event> Event> 我得到了这个异常：

MicroKernel.Handlers.GenericHandlerTypeMismatchException'发生在Castle.Windsor.dll中，但未在用户代码中处理。

其他信息：类型Queries.GetById'1 [[Models.Event， Domain，Version = 1.0.0.0，Culture = neutral，PublicKeyToken = null]]，Models.Event不满足组件'Queries.GetByIdHandler'1'的实现类型Queries.GetByIdHandler'1的通用约束。这很可能是你的代码中的一个bug。

它看起来类型已经成功注册，并且约束满足我可以告诉（ Event 是一个类并实现 IIdentity ）。我在这里错过了什么？我试图做一些温莎无法应对的事情吗？

，就像一些有用的信息，对于评论太多了。）

尽管Castle中的这段代码失败：

  public void Resolve_GetByIdHandler_Succeeds（）
 {
 var container = new Castle.Windsor.WindsorContainer（）; 
 $ b container.Register（Component 
.For（typeof（IQueryHandler<，>））
 .ImplementedBy（typeof（GetByIdHandler<>）））; 
 
 var x = container.Resolve< IQueryHandler< GetById< Event> ;, Event>>（）; 
 
  

Simple Injector 的工作原理：

  public void GetInstance_GetByIdHandler_Succeeds（）
 { 
 var container = new SimpleInjector.Container（）; 
 
 container.RegisterOpenGeneric（
 typeof（IQueryHandler<，>），
 typeof（GetByIdHandler<>））; 
 
 var x = container.GetInstance< IQueryHandler< GetById< Event> ;, Event>>（）; 
} 
  

I have two interfaces:

public interface IQuery<TResult> { }

public interface IQueryHandler<in TQuery, out TResult>
    where TQuery : IQuery<TResult>
{
    TResult Handle(TQuery q);
}

An example of a closed implementation of IQueryHandler:

public class EventBookingsHandler : IQueryHandler<EventBookings, IEnumerable<EventBooking>>
{
    private readonly DbContext _context;

    public EventBookingsHandler(DbContext context)
    {
        _context = context;
    }

    public IEnumerable<EventBooking> Handle(EventBookings q)
    {
        return _context.Set<MemberEvent>()
            .OfEvent(q.EventId)
            .AsEnumerable()
            .Select(EventBooking.FromMemberEvent);
    }
}

I can register and resolve closed generic implementations of IQueryHandler<,> with this component registration:

Classes.FromAssemblyContaining(typeof(IQueryHandler<,>))
    .BasedOn(typeof(IQueryHandler<,>))
    .WithServiceAllInterfaces()

However what I would like to do is resolve an open generic implementation that is "half closed" (ie specifies a generic TQuery type parameter):

public class GetById<TEntity> : IQuery<TEntity> where TEntity : class, IIdentity
{
    public int Id { get; private set; }

    public GetById(int id)
    {
        Id = id;
    }
}

public class GetByIdHandler<TEntity> : IQueryHandler<GetById<TEntity>, TEntity> where TEntity : class, IIdentity
{
    private readonly DbContext _context;

    public GetByIdHandler(DbContext context)
    {
        _context = context;
    }

    public TEntity Handle(GetById<TEntity> q)
    {
        return _context.Set<TEntity>().Find(q.Id);
    }
}

When I tried to resolve IQueryHandler<GetById<Event>, Event> I got this exception:

An exception of type 'Castle.MicroKernel.Handlers.GenericHandlerTypeMismatchException' occurred in Castle.Windsor.dll but was not handled in user code

Additional information: Types Queries.GetById'1[[Models.Event, Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], Models.Event don't satisfy generic constraints of implementation type Queries.GetByIdHandler'1 of component 'Queries.GetByIdHandler'1'. This is most likely a bug in your code.

It looks like the type has successfully registered, and the constraints are satisfied as far as I can tell (Event is a class and implements IIdentity). What am I missing here? Am I trying to do something that Windsor can't cope with?

解决方案

(I'm not posting this up as an answer, just as some useful information that is too much info for a comment.)

While this code in Castle fails:

public void Resolve_GetByIdHandler_Succeeds()
{
    var container = new Castle.Windsor.WindsorContainer();

    container.Register(Component
        .For(typeof(IQueryHandler<,>))
        .ImplementedBy(typeof(GetByIdHandler<>)));

    var x = container.Resolve<IQueryHandler<GetById<Event>, Event>>();
}

The same thing in Simple Injector works:

public void GetInstance_GetByIdHandler_Succeeds()
{
    var container = new SimpleInjector.Container();

    container.RegisterOpenGeneric(
        typeof(IQueryHandler<,>),
        typeof(GetByIdHandler<>));

    var x = container.GetInstance<IQueryHandler<GetById<Event>, Event>>();
}

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