如何通过Mapster接口代码生成实现IEnumerable到IDictionary的正确映射？

我想把这段手动映射代码：

var group = new Group {
    Participants = family.Children.ToDictionary(child => $"{child.LastName}, {child.FirstName}", child =>
        new Participant
        {
            Class = child.Age,
        })
};

替换为使用Mapster框架的实现：var camp = new UnitMapper().Map(family)，但不知道该如何配置才能让Dictionary的映射正确执行。

当前我的代码如下：

[Mapper]
public interface IUnitMapper {
    Group Map(Family family);
}

public class MappingRegistration : IRegister {
    public void Register(TypeAdapterConfig config) {
        config.NewConfig<Family, Group>()
            .Map(to => to.Participants, from => from.Children)
            ;
        
        config.NewConfig<Child, Participant>()
            .Map(to => to.Class, from => from.Age)
            ;
    }
}

public class Family {
    public IEnumerable<Child> Children { get; set; }
}

public class Child {
    public string FirstName { get; init; }
    public string LastName { get; init; }
    public int Age { get; init; }
}

public class Group {
    public IDictionary<string, Participant> Participants { get; set; }
}

public class Participant {
    public int Class { get; set; }
}

你需要在Family到Group的映射配置中，明确指定Dictionary的键生成规则，同时结合已有的Child到Participant的映射配置。修改MappingRegistration类的Register方法即可：

public class MappingRegistration : IRegister {
    public void Register(TypeAdapterConfig config) {
        // 保留Child到Participant的映射配置
        config.NewConfig<Child, Participant>()
            .Map(to => to.Class, from => from.Age);
        
        // 修改Family到Group的映射，指定Participants的转换逻辑
        config.NewConfig<Family, Group>()
            .Map(to => to.Participants, from => 
                from.Children.AdaptToDictionary(
                    child => $"{child.LastName}, {child.FirstName}", // Dictionary的键生成规则
                    child => child.Adapt<Participant>() // 复用已配置的Child到Participant映射
                )
            );
    }
}

说明 #

• AdaptToDictionary是Mapster提供的扩展方法，可直接将IEnumerable转换为Dictionary，需传入键的生成表达式和值的转换表达式。
• 由于已提前配置Child到Participant的映射规则，child.Adapt<Participant>()会自动复用该规则，无需重复编写Class = child.Age的逻辑。
• 完成配置后，调用new UnitMapper().Map(family)即可生成和手动映射完全一致的Group对象。

内容的提问来源于stack exchange，提问作者Tar