如何将两种泛型类型传递给扩展方法 [英] How to pass two generics types into an extension method

问题描述

我创建了以下扩展方法:

I've created the following extension method:

public static T Map<TEntity,T>(this TEntity entity) where TEntity : IEntity
{
    return Mapper.Map<TEntity, T>(entity);        
}

这允许以下操作:

Db.ExchangeSets.FirstOrDefault().Map<ExchangeSet, ExchangeSetSimpleViewModel>()

但是我想知道是否仍然可以修改扩展方法，以便可以按以下方式调用简短版本:

However i'm wondering if there is anyway I can modify the extension method so i can call a shorted version as follows:

Db.ExchangeSets.FirstOrDefault().Map<ExchangeSetSimpleViewModel>()

请注意:

是否应该使用automapper这样的问题不在问题范围之内，而更多的是事实调查任务.

Whether or not automapper should be used like this is not in the scope of the question, it's more a fact finding mission.

更新

对于那些在家中玩耍的人，借助Scott的评论，我设法在

For those of you playing at home, with the help of Scott's comment I managed to find an additional solution for the above function at Generic extension method for automapper.

public static T Map<T>(this IEntity entity) 
{
    return (T)Mapper.Map(entity, entity.GetType(), typeof(T));  
}

推荐答案

如果您想知道为什么为什么这是不可能的，我想问题在于模棱两可:

In case you are wondering why this is just not possible, I'd think the problem lies with ambiguity:

public static T Map<TEntity,T>(this TEntity entity) where TEntity : IEntity
{
    return Mapper.Map<TEntity, T>(entity);        
}

public static T Map<T>(this ExchangeSet set)
{
    // ...
}

那么，哪个方法被调用?请记住，这只是一个简单的示例.很有可能将来会实现部分类型推断，但是我想当涉及重载解析时，它会太令人困惑，并且成本/收益将完全失控.再说一次，这只是猜测.

So, which method gets called? Keep in mind this is just a simple example. It's very well possible that there could be a future implementation of partial type inference, but I'd imagine it would be too confusing when it comes to overload resolution and the cost/benefit would be completely out of control. Then again, that's just speculation.

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