Automapper: complex if else statement in ForMember

Question

Assuming the Date is a nullable DateTime:

Mapper.CreateMap<SomeViewModels, SomeDTO>()                             .ForMember(dest => dest.Date,                         opt => opt.MapFrom(src =>                         {                             DateTime? finalDate = null;                             if (src.HasDate == "N")                             {                                 // so it should be null                             }                             else                             {                                                                    endResult = DateTime.Parse(src.Date.ToString());                                                              }                                                            return finalDate;                          })); 

The error I got was:

Error 30 A lambda expression with a statement body cannot be converted to an expression tree.

Of course I'm fully aware that I can simplify the query such as:

Mapper.CreateMap<SomeViewModels, SomeDTO>()              .ForMember(dest => dest.Date,                         opt => opt.MapFrom(src => src.HasDate == "N" ? null : DateTime.Parse(src.Date.ToString())));      

But what if I insist to retain the structure of the first example, because I have more complicated if else statements, that the second example will not able to cater for, or at least will not be very readable?

Answer 1

In recent versions of AutoMapper, ResolveUsing was removed. Instead, use a new overload of MapFrom:

void MapFrom<TResult>(Func<TSource, TDestination, TResult> mappingFunction); 

Just adding another lambda/function parameter will dispatch to this new overload:

        CreateMap<TSource, TDest>()                 .ForMember(dest => dest.SomeDestProp, opt => opt.MapFrom((src, dest) =>                 {                     TSomeDestProp destinationValue;                      // mapping logic goes here                      return destinationValue;                 }));