使用泛型的AutoMapper ResolveUsing会导致“提供的值是X类型但预期Y类型”错误

Question

我有一种情况，我必须使用AutoMapper将DTO映射到域对象。 这种映射需要一些复杂的管理，所以我创建了一个自定义值解析器。 我想从FooDTO获得Foo 。 这两个对象之间的唯一区别是Foo具有ICollection<Child> ， FooDTO具有TrackedData<ChildDTO> ，其中TrackeData<T>是具有3 ICollection<T>的对象。 这是我的简化方案：

public class TrackedData<T>
{
    public ICollection<T> Updated { get; set; }
    public ICollection<T> Created { get; set; }
    public ICollection<T> Deleted { get; set; }

    public TrackedData()
    {
        Updated = new List<T>();
        Created = new List<T>();
        Deleted = new List<T>();
    }
}

public class Foo
{
    private List<Child> _childs;

    public string Name { get; set; }
    public ICollection<Child> Childs
    {
        get
        {
            if (_childs == null)
                _childs = new List<Child>();
            return _childs;
        }
        set
        {
            _childs = (List<Child>)value;
        }
    }
}

public class Child
{
    public string Description { get; set; }
}

public class FooDTO
{
    public string Name { get; set; }
    public TrackedData<ChildDTO> Childs { get; set; }
}

public class ChildDTO
{
    public string Description { get; set; }
}

public class Program
{
    public static void Main(string[] args)
    {
        Mapper.CreateMap(typeof(TrackedData<>), typeof(TrackedData<>));
        Mapper.CreateMap<ChildDTO, Child>();
        Mapper.CreateMap<FooDTO, Foo>()
            .ForMember(d => d.Childs, opt => opt.ResolveUsing<TrackedDataResolver<ChildDTO, Child>>());

        FooDTO fooDTO = CreateFakeFooDTO();

        Foo foo = Mapper.Map<FooDTO, Foo>(fooDTO);
    }

    private static FooDTO CreateFakeFooDTO() { /* omitted for simplicity */ }

    private static TrackedData<ChildDTO> CreateFakeTrackedDataChildDTO() { /* omitted for simplicity */ }

    private static ICollection<ChildDTO> CreateFakeListChildDTO() { /* omitted for simplicity */ }

    private static ChildDTO CrateFakeChildDTO(){ /* omitted for simplicity */ }
}

public class TrackedDataResolver<TSource, TDestination> : ValueResolver<TrackedData<TSource>, ICollection<TDestination>>
{
    protected override ICollection<TDestination> ResolveCore(TrackedData<TSource> source)
    {
        TrackedData<TDestination> trackedDestination = new TrackedData<TDestination>();
        ICollection<TDestination> destination = new List<TDestination>();

        trackedDestination = Mapper.Map<TrackedData<TSource>, TrackedData<TDestination>>(source);

        foreach (var o in trackedDestination.Created)
        {
            // Do stuff...
            destination.Add(o);
        }
        foreach (var o in trackedDestination.Updated)
        {
            // Do stuff...
            destination.Add(o);
        }
        foreach (var o in trackedDestination.Deleted)
        {
            // Do stuff...
            destination.Add(o);
        }

        return destination;
    }
}

执行此行时

Foo foo = Mapper.Map<FooDTO, Foo>(fooDTO);

我收到此错误：

{“提供的值是AutoMapperDemo.FooDTO类型，但应为AutoMapperDemo.TrackedData'1 [AutoMapperDemo.ChildDTO]。更改值解析器源类型，或使用FromMember将提供的源值重定向到值解析器。\\ r \\ n提供的值是键入AutoMapperDemo.FooDTO，但期望的是AutoMapperDemo.TrackedData'1 [AutoMapperDemo.ChildDTO]。更改值解析器的源类型，或使用FromMember将提供的源值重定向到值解析器。“}

Github中提供了源代码 ： https : //github.com/josmonver/AutoMapperValueResolverIssue.git任何想法我为什么会收到此错误？

Answer 1

您可以在TrackedData<T>类中实现类似于UnionAll方法（更新+创建+删除）的方法，然后映射它：

    Mapper.CreateMap<FooDTO, Foo>()
        .ForMember(d => d.Childs, opt => opt.MapFrom(src => src.UnionAll()));