Automapper: bidirectional mapping with ReverseMap() and ForMember()

I have the case where I want to map an entity to a viewmodel and back. I have to specify the mapping explicitly with ForMember() because their properties do not share the exact same names. Here is a short example of how my classes look like:

public class PartTwo {
    public int Integer { get; set; }
}

public class PartTwoViewModel {
    public int PartInteger { get; set; }
}

And I want to use them this way:

Mapper.CreateMap<PartTwo, PartTwoViewModel>()
    .ForMember(dst => dst.PartInteger, opt => opt.MapFrom(src => src.Integer))
    .ReverseMap();

var partTwoViewModel = new PartTwoViewModel() { PartInteger = 42 };
var partTwo = Mapper.Map<PartTwoViewModel, PartTwo>(partTwoViewModel);
Assert.AreEqual(partTwoViewModel.PartInteger, partTwo.Integer);

But it does not match the property PartInteger to Integer. (Integer is 0.)

Is there a way to make this work? (When the properties of both classes have the same names it works.) Do I have to set some kind of option in the method ForMember()?

ReverseMap returns an IMappingExpression that represents the reversal of the mapping. Once you call, it subsequent calls will be for configuring the reversal of the map.

Here's an example:

Mapper.CreateMap<CartItemDto, CartItemModel>()
      .ForMember(dest => dest.ExtendedCost, opt => opt.Ignore())
      .ReverseMap()
          .ForMember(dest => dest.Pricing, opt => opt.Ignore())

This will ignore the Pricing field in the reverse direction.

You could define your configuration like this:

Mapper.CreateMap<PartTwo, PartTwoViewModel>()
    .ForMember(dst => dst.PartInteger, opt => opt.MapFrom(src => src.Integer));

Mapper.CreateMap<PartTwoViewModel, PartTwo>()
    .ForMember(dst => dst.Integer, opt => opt.MapFrom(src => src.PartInteger));

UPDATE

Here is the commit where ReverseMap was initially implemented. From what I can see in the code, it only creates a simple reverse mapping. For example, in this case it would automatically configure the equivalent of:

Mapper.CreateMap<PartTwoViewModel, PartTwo>();

To get anything more complex, I'm afraid that you're going to have to configure it manually.