使用Automapper从嵌套了多层的列表中映射/转换为父属性

// 定义源对象
public class SourceObject
{
    public List<List<int>> NestedList { get; set; }
}

// 定义目标对象
public class DestinationObject
{
    public List<int> FlatList { get; set; }
}

// 配置映射规则
var config = new MapperConfiguration(cfg =>
{
    cfg.CreateMap<List<List<int>>, List<int>>()
        .ConvertUsing(source => source.SelectMany(x => x).ToList());
    cfg.CreateMap<SourceObject, DestinationObject>()
        .ForMember(dest => dest.FlatList, opt => opt.MapFrom(src => src.NestedList));
});

// 创建映射器
var mapper = new Mapper(config);

// 进行对象转换
var source = new SourceObject
{
    NestedList = new List<List<int>>
    {
        new List<int> { 1, 2, 3 },
        new List<int> { 4, 5, 6 },
        new List<int> { 7, 8, 9 }
    }
};

var destination = mapper.Map<DestinationObject>(source);

// 输出结果
Console.WriteLine(string.Join(", ", destination.FlatList)); // 输出：1, 2, 3, 4, 5, 6, 7, 8, 9