如何利用Automapper将ProjectTo与地图相结合？
如何利用Automapper将ProjectTo与地图相结合？
提问于 2022-03-25 11:20:14
为了简短起见，这里有数据库实体：
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; }
}这些被EF Core 6正确地映射到TPH。当读取返回值时，我们得到ClientAddressFact和ClientAddressRegistered对应于Client.Addresses内部的AddressType。
现在，我需要将这些转换为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无法工作，因为无法在LINQ之外构造正确的SELECT语句并创建相应的实体类型。因此，我们的想法是第一个ProjectTo地址列表，如下所示：
public record ClientAddressCommon : ClientAddress
{
public string SpecificValue_Fact { get; init; }
public string SpecificValue_Registered { get; init; }
}然后用Map来纠正实体类型，这样最终我就可以得到正确的Client DTO，并在Addresses中填充正确的ClientAddressFact和ClientAddressRegistered。
但问题是，如何使用单个ProjectTo调用而只使用概要文件来实现呢？问题是投影代码与使用它的多个概要文件项目是分开的。
以下是其中一个简介：
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()可以让我正确地填充Client，但只能使用ClientAddressCommon地址。那么如何在第二步使用Map的全部功能来转换它们呢？
UPDATE_01:
根据卢西恩·巴戈阿努的comment，我做了一些调整：
var projected = _mapper.ProjectTo<Models.Client>(filtered).Single();
var mapped = _mapper.Map<Models.Client>(projected);但不知道该怎么做。以下是更新的个人资料：
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，以转换投影所留下的内容。在这种情况下，我需要将ClientAddressCommon映射到ClientAddressFact或基于AddressType的ClientAddressRegistered。但看起来地图没被用过。我现在少了什么？
回答 1
Stack Overflow用户
回答已采纳
发布于 2022-03-27 12:34:22
这就是我想出来的。ClientAddress现在看起来是这样的：
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>()
;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))
};这就是最后的转换方式：
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，投影后我还需要重新映射：
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这一切似乎都奏效了，但我不完全确定这是否是正确的做事方式。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/71616100
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