通过与AutoMapper的接口推断目标类型 [英] Inferring destination type from interface with AutoMapper

问题描述

我正在尝试在应用程序中实现一些横切关注点，该应用程序使用AutoMapper在不同的DTO/消息对象之间进行映射.

说我有这个: configuration.Map<MyMessage, MyEvent>(). MyEvent实现IEvent(这是没有属性的标记接口).是否有任何方法可以要求AutoMapper将MyMessage映射到IEvent，并推断出哦，我将MyMessage映射到MyEvent，并且MyEvent实现了IEvent""?

这个(无效的)示例显示了我想要实现的目标:

// IEvent is just a marker interface with no properties,
// and is implemented by all of the *Event classes

configuration.CreateMap<MyMessage, MyEvent>();
configuration.CreateMap<MyOtherMessage, MyOtherEvent>();
// etc.

// ... somewhere else in the code ...

public class MyCrossCuttingThing<TMessage>
{
    private readonly IMapper _mapper;

    // ... code that does stuff ...

    public void DoThing(TMessage message)
    {
        // ... more code ...

        var @event = _mapper.Map<IEvent>(message);

        // Here I would expect @event to be a MyEvent instance if
        // TMessage is MyMessage, for example
    }
}

这给了我一个例外:

缺少类型映射配置或不支持的映射.

我尝试将.Include或.IncludeBase添加到CreateMap语句，但是结果相同.有什么方法可以实现我想要的，还是这根本不是受支持的用例?

解决方案

在这种简单情况下，您可以使用As.

CreateMap<MyMessage, IEvent>().As<MyEvent>();

鉴于IEvent是标记接口，您还需要具体的地图MyMessage => MyEvent. 如果实际情况更复杂，则需要包括. 文档.

I'm trying to implement some cross-cutting concerns in my application, which uses AutoMapper to map between different DTOs/message objects.

Say I have this: configuration.Map<MyMessage, MyEvent>(). MyEvent implements IEvent (which is a marker interface with no properties). Is there any way to ask AutoMapper to map a MyMessage to IEvent, and have it infer that "oh, I have a mapping MyMessage to MyEvent, and MyEvent implements IEvent"?

This (invalid) example shows what I want to achieve:

// IEvent is just a marker interface with no properties,
// and is implemented by all of the *Event classes

configuration.CreateMap<MyMessage, MyEvent>();
configuration.CreateMap<MyOtherMessage, MyOtherEvent>();
// etc.

// ... somewhere else in the code ...

public class MyCrossCuttingThing<TMessage>
{
    private readonly IMapper _mapper;

    // ... code that does stuff ...

    public void DoThing(TMessage message)
    {
        // ... more code ...

        var @event = _mapper.Map<IEvent>(message);

        // Here I would expect @event to be a MyEvent instance if
        // TMessage is MyMessage, for example
    }
}

This gives me an exception:

Missing type map configuration or unsupported mapping.

I've tried adding .Include or .IncludeBase to the CreateMap statement, but same result. Is there any way to achieve what I want, or is this simply not a supported use case?

解决方案

For this simple case you can use As.

CreateMap<MyMessage, IEvent>().As<MyEvent>();

Given that IEvent is a marker interface, you need also the concrete map MyMessage=>MyEvent. If your real case is more complicated, you need Include. The docs.

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