AutoMapper 到 map 嵌套列表 object

Question

I have 2 objects: Parent and ParentDTO:

class ParentDTO
    {
        public string AttA { get; set; }
        public List<List<BDto>> AttrBNestedList { get; set; }
    }
    class BDto
    {
        public string AttrC { get; set; }
        public int AtterD { get; set; }
        public string AtterE { get; set; }

        public CDto AttrFobj { get; set; }
    }

    class CDto
    {
        public string AttrG { get; set; }
        public int AtterH { get; set; }
    }

    //--------------------------------------
    class Parent 
    {
        public string AttA { get; set; }
        public List<B> AttrBList { get; set; }
    }
    class B
    {
        public string AttrC { get; set; }
        public int AtterD { get; set; }
        public string AtterE { get; set; }

        public C AttrFobj { get; set; }
        public C AttrGobj { get; set; }
        public C AttrHobj { get; set; }

    }

    class C
    {
        public string AttrI { get; set; }
        public string AttrJ { get; set; }
        public int AtterK { get; set; }
    }

I want to using AutoMapper to map data from ParentDto object to Parent object (all data in ParentDto has to transfer to Parent, but first element from AttrBNestedList copy to AttrBList)

Mapper.CreateMap<CDto, C>();
Mapper.CreateMap<BDto, B>();
Mapper.CreateMap<ParentDto, Parent>()
      .ForMember(dest => dest.AttrBList , opt => opt.AttrBNestedList.singleorDefault??);

I need just singleorDefault item from List<List<BDto>> AttrBNestedList map to List<B> AttrBList

Can anyone help me. Thanks

Answer 1

There is a syntax error which doesn't allow you to use SingleOrDefault() , you need to use MapFrom method:

Mapper.CreateMap<ParentDTO, Parent>().ForMember(dest => dest.AttrBList, opt => opt.MapFrom(src => src.AttrBNestedList.SingleOrDefault()));