将对象传递给 AutoMapper 映射

Question

我正在使用 AutoMapper，被映射到的实体的一些值是我当前方法中的变量。我已经尝试谷歌它但无济于事。我可以将一组 KeyValue Pairs 或一个对象或其他东西传递给我的映射以让它使用这些值吗？

后期映射修改示例

//comment variable is a Comment class instance
var imageComment = AutoMapper.Mapper.Map<Data.ImageComment>(comment);
//I want to pass in imageId so I dont have to manually add it after the mapping
imageComment.ImageId = imageId;

Answer 1

AutoMapper 9.0.0

从 8.0.0 版开始，AutoMapper 的 API 已更改。在这样做时，ResolveUsing 与MapFrom 合并。更多信息请查看相应的pull request。

个人资料

public class CoreProfile : Profile
{
    public CoreProfile()
    {
        CreateMap<Source, Destination>()
            .ForMember(d => d.Bar,
                opt => opt.MapFrom(
                    (src, dst, _, context) => context.Options.Items["bar"]
                )
            );    
    }
}

映射

var destination = mapper.Map<Destination>(
    source,opt => {
        opt.Items["bar"] = "baz";
    }
);

Answer 2

可以使用Items Dictionary 选项将对象传递给解析器。执行此操作的标准 API 非常冗长（如已接受的答案所示），但可以使用一些扩展方法很好地简化：

/// <summary>
/// Map using a resolve function that is passed the Items dictionary from mapping context
/// </summary>
public static void ResolveWithContext<TSource, TDest, TMember, TResult>(
    this IMemberConfigurationExpression<TSource, TDest, TMember> memberOptions, 
    Func<TSource, IDictionary<string, object>, TDest, TMember, TResult> resolver
) {
    memberOptions.ResolveUsing((src, dst, member, context) => resolver.Invoke(src, context.Items, dst, member));
}

public static TDest MapWithContext<TSource, TDest>(this IMapper mapper, TSource source, IDictionary<string, object> context, Action<IMappingOperationOptions<TSource, TDest>> optAction = null) {
    return mapper.Map<TSource, TDest>(source, opts => {
        foreach(var kv in context) opts.Items.Add(kv);
        optAction?.Invoke(opts);
    });
}

可以这样使用：

// Define mapping configuration
Mapper.CreateMap<Comment, ImageComment>()
    .ForMember(
        d => d.ImageId,
        opt => opt.ResolveWithContext(src, items, dst, member) => items["ImageId"])
    );

// Execute mapping
var context = new Dictionary<string, object> { { "ImageId", ImageId } };
return mapper.MapWithContext<TSource, TDest>(source, context);

如果您有一个通常需要传递给映射器解析器的对象（例如，当前用户），您可以更进一步，定义更专业的扩展：

public static readonly string USER_CONTEXT_KEY = "USER";

/// <summary>
/// Map using a resolve function that is passed a user from the
/// Items dictionary in the mapping context
/// </summary>
public static void ResolveWithUser<TSource, TDest, TMember, TResult>(
    this IMemberConfigurationExpression<TSource, TDest, TMember> memberOptions,
    Func<TSource, User, TResult> resolver
) {
    memberOptions.ResolveWithContext((src, items, dst, member) =>
        resolver.Invoke(src, items[USER_CONTEXT_KEY] as User));
}

/// <summary>
/// Execute a mapping from the source object to a new destination
/// object, with the provided user in the context.
/// </summary>
public static TDest MapForUser<TSource, TDest>(
    this IMapper mapper,
    TSource source,
    User user,
    Action<IMappingOperationOptions<TSource, TDest>> optAction = null
) {
    var context = new Dictionary<string, object> { { USER_CONTEXT_KEY, user } };
    return mapper.MapWithContext(source, context, optAction);
}

可以这样使用：

// Create mapping configuration
Mapper.CreateMap<Source, Dest>()
    .ForMember(d => d.Foo, opt => opt.ResolveWithUser((src, user) src.Foo(user));

// Execute mapping
return mapper.MapWithUser(source, user);

Answer 3

对于 Automapper 6.0.2：

简介：

public class CoreProfile : Profile
{
    public CoreProfile()
    {
        CreateMap<Source, Dest>()
            .ForMember(d => d.Foo,
                opt => opt.ResolveUsing(
                    (src, dst, arg3, context) => context.Options.Items["Foo"]
                )
            );
    }
}

映射：

    var result = Mapper.Map<PlanResult>(aa, opt => {
        opt.Items["Foo"] = 2;
        opt.Items["OtherFoo"] = 1000;
    });

Answer 4

AutoMapper 开箱即用地处理这种键值对场景。

Mapper.CreateMap<Source, Dest>()
    .ForMember(d => d.Foo, opt => opt.ResolveUsing(res => res.Context.Options.Items["Foo"]));

然后在运行时：

Mapper.Map<Source, Dest>(src, opt => opt.Items["Foo"] = "Bar");

深入研究上下文项目有点冗长，但你去吧。

Answer 5

假设你有这两个对象：

public class ObjectA {
 public string Property1 { get; set; }
 public int Property2 { get; set; }
}
public class ObjectB {
 public string Property1 { get; set; }
 public int Property2 { get; set; }
}

如果您想将ObjectA 类型的现有对象复制到ObjectB 类型的新对象中，您必须使用 AutoMapper 执行此操作：

var objectA = new ObjectA { Property1 = "Hello, World!", Property2 = 1 }
var objectB = new ObjectB();

// Copy data from a to b
AutoMapper.Mapper
  .CreateMap<ObjectA, ObjectB>()
  .BeforeMap((source, dest) => { dest.ImageId = imageId });
AutoMapper.Mapper.Map(objectA, objectB); // source, destination;

// Or:
var objectB = AutoMapper.Mapper.Map<ObjectB>(objectA);