Automapper接口映射

Question

我有 PagedList 实现，并且尝试使用 AutoMapper 将实体 PagedList 映射到 DTO PagedList。

这是我的界面：

public interface IPagedList<T> : IList<T>
{
    PagingInformation Paging { get; set; }
}

这是我的班级实施：

public class PagedList<T> : List<T>, IPagedList<T> //, IList<T>
{
    public PagingInformation Paging { get; set; }

    public PagedList()
    {
    }

    public PagedList(IEnumerable<T> collection) : base(collection)
    {
    }

    public PagedList(IEnumerable<T> collection, PagingInformation paging) : base(collection)
    {
        Paging = paging;
    }

    public PagedList(int capacity) : base(capacity)
    {
    }

    PagingInformation IPagedList<T>.Paging
    {
        get => Paging;
        set => Paging = value;
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }


}

我正在使用 Automapper 像

public async Task<DomainResult<IPagedList<PositionDto>>> GetPagedListAsync(int pageIndex = 0, int pageSize = 20)
{
    return DomainResult<IPagedList<PositionDto>>.Success(_mapper.Map<IPagedList<PositionDto>>(await _positionRepository.GetPagedListAsync(pageIndex, pageSize)));
}

没有映射器配置：我收到以下错误：

映射类型错误。

映射类型：PagedList 1 -> IPagedList1 WestCore.Shared.Collections.Pagination.PagedList 1[[WestCore.Domain.Entities.Position, WestCore.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] -> WestCore.Shared.Collections.Pagination.IPagedList1[[WestCore.AppCore.Models.PositionDto, WestCore.AppCore, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]

当我添加CreateMap(typeof(PagedList<>), typeof(IPagedList<>))到 Mapper Pofile 时，出现以下错误：

类型“代理 WestCore.Shared.Collections.Pagination.IPgedList`1[[WestCore.AppCore.Models.PositionDto_WestCore.AppCore_Version=1.0.0.0_Culture=neutral_PublicKeyToken=null]]_WestCore.Shared_Version=1.0.0.0_Culture= 中的方法“get_Item”程序集“AutoMapper.Proxies，Version=0.0.0.0，Culture=neutral，PublicKeyToken=be96cd2c38ef1005”中的中性_PublicKeyToken = null'没有实现。

当我添加CreateMap(typeof(PagedList<>),typeof(IPagedList<>)).As(typeof(PagedList<>));到 Mapper Profile 时，我没有收到错误，但 PagedList 返回空结果集

我不确定我是否缺少PagedList方法的实现或者这是一个配置问题。

编辑：

添加分页信息如下：

    public class PagingInformation
{
    /// <summary>
    /// Gets the index start value.
    /// </summary>
    /// <value>The index start value.</value>
    public int IndexFrom { get; }

    /// <summary>
    /// Gets the page index (current).
    /// </summary>
    public int PageIndex { get; }

    /// <summary>
    /// Gets the page size.
    /// </summary>
    public int PageSize { get; }

    /// <summary>
    /// Gets the total count of the list of type <typeparamref name="TEntity"/>
    /// </summary>
    public int TotalCount { get; }

    /// <summary>
    /// Gets the total pages.
    /// </summary>
    public int TotalPages { get; }

    /// <summary>
    /// Gets the has previous page.
    /// </summary>
    /// <value>The has previous page.</value>
    public bool HasPreviousPage => PageIndex - IndexFrom > 0;

    /// <summary>
    /// Gets the has next page.
    /// </summary>
    /// <value>The has next page.</value>
    public bool HasNextPage => PageIndex - IndexFrom + 1 < TotalPages;

    public PagingInformation(int pageIndex, int pageSize, int indexFrom, int count)
    {
        if (indexFrom > pageIndex)
        {
            throw new ArgumentException($"indexFrom: {indexFrom} > pageIndex: {pageIndex}, must indexFrom <= pageIndex");
        }

        PageIndex = pageIndex;
        PageSize = pageSize;
        IndexFrom = indexFrom;
        TotalCount = count;
        TotalPages = (int) Math.Ceiling(TotalCount / (double) PageSize);

    }
}

谢谢

Answer 1

您不能使用接口作为映射的结果，因为映射器不知道如何创建它。

您可以使用 ConstructUsing 创建 IPgedList。像这样：

AutoMapper.Mapper.CreateMap<DtoParent, ICoreParent>()
            .ConstructUsing(parentDto => new CoreParent())
            .ForMember(dest => dest.Other, opt => opt.MapFrom(src => AutoMapper.Mapper.Map<DtoChild, ICoreChild>(src.Other)));

编辑：

这样工作：

class Example
{
    static void Main()
    {
        AutoMapper.Mapper.Initialize(config =>
        {
            config.CreateMap(typeof(PagedList<>), typeof(IPagedList<>))
                 .ConvertUsing(typeof(Converter<,>));

            config.CreateMap<Entity, DTO>();

        });

        var entityList = new PagedList<Entity>(new [] { new Entity(), }, new PagingInformation() { Total =  2, PageNumber =  1, PageSize = 10});

        var mapped = Mapper.Map<IPagedList<DTO>>(entityList);
    }
}

class Converter<TSource, TDest> : ITypeConverter<IPagedList<TSource> , IPagedList<TDest>>
{
    public IPagedList<TDest> Convert(IPagedList<TSource> source, IPagedList<TDest> destination, ResolutionContext context) =>  new PagedList<TDest>(context.Mapper.Map<IEnumerable<TDest>>(source.AsEnumerable()), source.Paging);
}

class Entity
{
    public Guid Id { get; set; } = Guid.NewGuid();
}

class DTO
{
    public Guid Id { get; set; } = Guid.NewGuid();
}

public interface IPagedList<T> : IList<T>
{
    PagingInformation Paging { get; set; }
}

public class PagingInformation
{
    public int Total { get; set; }

    public int PageSize { get; set; }

    public int PageNumber { get; set; }
}

public class PagedList<T> : List<T>, IPagedList<T>
{
    public PagingInformation Paging { get; set; }

    public PagedList() { }
    public PagedList(IEnumerable<T> collection) : base(collection) { }

    public PagedList(IEnumerable<T> collection, PagingInformation paging) : base(collection) { Paging = paging; }
}

也可能需要以某种其他方式映射 PagingInformation，如在我的示例中，两个分页列表都在映射后引用一个 PagingInformation 对象，我认为在 PagingInformation 不可变之前这是可以的。