如何使用 Automapper 将 ProjectTo 与 Map 结合起来？

Question

简而言之，这里是数据库实体：

public class Client
{
    [Key]
    public int Id { get; set; }

    [Required]
    public string Name { get; set; }

    public ICollection<ClientAddress> Addresses { get; set; }
}

public abstract class ClientAddress : ClientSubEntityBase
{
    public int ClientId { get; set; }

    [Required]
    public virtual AddressType AddressType { get; protected set; }

    [Required]
    public string Address { get; set; }
}

public enum AddressType
{
    Fact = 1,
    Registered = 2,
}

public class ClientAddressFact : ClientAddress
{
    public override AddressType AddressType { get; protected set; } = AddressType.Fact;
    public string SpecificValue_Fact { get; set; }
}
public class ClientAddressRegistered : ClientAddress
{
    public override AddressType AddressType { get; protected set; } = AddressType.Registered;
    public string SpecificValue_Registered { get; set; }
}

这些由 EF Core 6 正确映射到 TPH。当读回值时，我们得到 ClientAddressFact 和 ClientAddressRegistered 对应于 Client.Addresses.

中的 AddressType

现在我需要将它们转换为我的 DTO：

public record Client
{
    public string Name { get; init; }
    public IEnumerable<ClientAddress> Addresses { get; init; }
}

public abstract record ClientAddress
{
    public ClientAddressType AddressType { get; init; }
    public string Address { get; init; }
}

public enum ClientAddressType
{
    Fact,
    Registered,
}

public record ClientAddressFact : ClientAddress
{
    public string SpecificValue_Fact { get; init; }
}
public record ClientAddressRegistered : ClientAddress
{
    public string SpecificValue_Registered { get; init; }
}

显然使用 ProjectTo 是行不通的，因为无法从 LINQ 构造正确的 SELECT 语句并创建相应的实体类型。所以想法是首先 ProjectTo 地址列表到这样的东西：

public record ClientAddressCommon : ClientAddress
{
    public string SpecificValue_Fact { get; init; }
    public string SpecificValue_Registered { get; init; }
}

然后 Map 这些来纠正实体类型所以最后我可以得到我正确的 Client DTO 并在 [=27] 中填充正确的 ClientAddressFact 和 ClientAddressRegistered =].

但问题是如何使用单个 ProjectTo 调用并且仅使用配置文件来做到这一点？问题是投影代码与使用它的多个配置文件项目是分开的。

这是个人资料之一：

private static Models.ClientAddressType ConvertAddressType(Database.Entities.Enums.AddressType addressType) =>
    addressType switch
    {
        Database.Entities.Enums.AddressType.Fact => Models.ClientAddressType.Fact,
        Database.Entities.Enums.AddressType.Registered => Models.ClientAddressType.Registered,

        _ => throw new ArgumentException("Unknown address type", nameof(addressType))
    };

CreateProjection<Database.Entities.Data.Client, Models.Client>()
;

CreateProjection<Database.Entities.Data.ClientAddress, Models.ClientAddress>()
    .ForMember(dst => dst.AddressType, opts => opts.MapFrom(src => ConvertAddressType(src.AddressType)))
    .ConstructUsing(src => new Models.ClientAddressCommon())
;

使用 var projected = _mapper.ProjectTo<Models.Client>(filtered).Single() 给我正确填写的 Client 但只有 ClientAddressCommon 地址。那么我如何在第二步使用 Map 的全部功能转换它们？

UPDATE_01:

根据 Lucian Bargaoanu 的我做了一些调整：

var projected = _mapper.ProjectTo<Models.Client>(filtered).Single();
var mapped = _mapper.Map<Models.Client>(projected);

但不确定如何进行。这是更新后的个人资料：

CreateMap<Models.Client, Models.Client>()
    .AfterMap((src, dst) => Console.WriteLine("CLIENT: {0} -> {1}", src, dst)) // <-- this mapping seems to work
;

CreateMap<Models.ClientAddressCommon, Models.ClientAddress>()
    .ConstructUsing(src => new Models.ClientAddressFact()) // simplified for testing
    .AfterMap((src, dst) => Console.WriteLine("ADR: {0} -> {1}", src, dst)) // <-- this is not outputting
;

基本上，我现在将 Client 映射到自身，只是为了转换投影剩下的部分。在这种情况下，我需要根据 AddressType“aftermap”ClientAddressCommon 到 ClientAddressFact 或 ClientAddressRegistered。但看起来没有使用映射。我现在缺少什么？

Answer 1

这就是我的想法。 ClientAddress 现在看起来像这样：

public record ClientAddress
{
    public ClientAddressType AddressType { get; init; } // <-- used to differentiate between address types
    public string Address { get; init; }
    public virtual string SpecificValue_Fact { get; init; } // <-- specific for ClientAddressFact
    public virtual string SpecificValue_Registered { get; init; } // <-- specific for ClientAddressRegistered
}

public record ClientAddressFact : ClientAddress
{
}
public record ClientAddressRegistered : ClientAddress
{
}

public enum ClientAddressType
{
    Fact,
    Registered,
}

配置文件如下所示：

CreateProjection<Database.Entities.Data.Client, Models.Client>() // <-- project from DB to DTO for the main entity
;

CreateProjection<Database.Entities.Data.ClientAddress, Models.ClientAddress>() // <-- project from TPH entity type to a type which holds all the common properties for all address types
    .ForMember(dst => dst.AddressType, opts => opts.MapFrom(src => ConvertAddressType(src.AddressType)))
;

CreateMap<Models.Client, Models.Client>() // <-- this is needed so AM knows that we need to map a type to itself
;

CreateMap<Models.ClientAddress, Models.ClientAddress>() // <-- changed destination type to itself, since it is the only one available at that moment after projection
    .ConvertUsing<ClientAddressTypeConverter>()
;

CreateMap<Models.ClientAddress, Models.ClientAddressFact>()
;
CreateMap<Models.ClientAddress, Models.ClientAddressRegistered>()
;

一个enum转换助手：

public static Models.ClientAddressType ConvertAddressType(Database.Entities.Enums.AddressType addressType) =>
    addressType switch
    {
        Database.Entities.Enums.AddressType.Fact => Models.ClientAddressType.Fact,
        Database.Entities.Enums.AddressType.Registered => Models.ClientAddressType.Registered,

        _ => throw new ArgumentException("Неизвестный address type", nameof(addressType))
    };

最后是这样转换的：

private class ClientAddressTypeConverter : ITypeConverter<Models.ClientAddress, Models.ClientAddress>
{
    public Models.ClientAddress Convert(Models.ClientAddress source, Models.ClientAddress destination, ResolutionContext context) =>
        source.AddressType switch
        {
            Models.ClientAddressType.Fact => context.Mapper.Map<Models.ClientAddressFact>(source),
            Models.ClientAddressType.Registered => context.Mapper.Map<Models.ClientAddressRegistered>(source),

            _ => throw new ArgumentException("Unknown address type")
        };
}

是的，投影后我还需要再次re-map：

var projected = _mapper.ProjectTo<Models.Client>(filtered).Single();
var mapped = _mapper.Map<Models.Client>(projected); // map from itself to itself to convert ClientAddress to corresponding sub-types

这一切似乎都有效，但我不完全确定这是否是正确的做事方式。

如何使用 Automapper 将 ProjectTo 与 Map 结合起来？

How to combine ProjectTo with Map using Automapper?

c#

type-conversion

automapper

tph

entity-framework-core