automapper post "ForMember" properties

Question

i'm new with automapper and i have a problem with navigation properties mapping. I have create a map like this :

CreateMap<ObjEntity, ObjEntityViewModel>()
                .ForMember(dest => dest.LabelName,
                    opts => opts.MapFrom(src => src.IdNavigation.LabelName)).ReverseMap();

it made a flat object and it works fine. But when i post back ObjEntityViewModel from my Edit Form, the property "LabelName" is always null. It appears all properties define with ForMember always null when it post back from my html form. I don't understand why is it null and how can i resolve this problem.

My controller code :

public MesObsIndividusController(IMapper mapper)
        {
            _mapper = mapper;            
        }

public async Task<IActionResult> Edit(int? id)
        {
            if (id == null)
            {
                return new NotFoundViewResult("NotFound");
            }

            var mesObsIndividus = await _observationService.GetMesObsindividus(id.Value);
            if (mesObsIndividus == null)
            {
                return new NotFoundViewResult("NotFound");
            }

            //mapping du ViewModel
            var mesVM = _mapper.Map<ObjEntityViewModel>(mesObsIndividus);

            return (mesVM);
}

        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Edit(int id, ObjEntityViewModel mesObsIndividus)            
        {
            if (id != mesObsIndividus.IdMes)
            {
                return new NotFoundViewResult("NotFound");
            }



            if (ModelState.IsValid){
                //do update database stuff

            }else
            {
                return View(mesObsIndividus);
            }
            return RedirectToAction(nameof(Details), new { id = mesObsIndividus.IdMes });
        }

My html code :

@model Proj.Models.ObjEntityViewModel
<form asp-action="Edit">
    <input type="hidden" asp-for="IdMes"  />

    <div class="form-group">
                <label asp-for="LibEspece" class="control-label"></label>
                <input asp-for="LibEspece" id="LbEspece" class="form-control" />
                <span asp-validation-for="LibEspece" class="text-danger"></span>
    </div>

    <dl class="dl-horizontal">
                <dt>
                    @Html.DisplayNameFor(model => model.LabelName)
                </dt>
                <dd>
                    @Html.DisplayFor(model => model.LabelName)
                </dd>
    </dl>

    <div class="form-group">
         <input type="submit" value="Enregistrer" class="btn btn-primary" />
    </div>
</form>

Thank's

I use EF core 2.2 and automapper 6.0.0

Answer 1

Your problem is that you don't persist the LabelName in your form.

Using @Html.DisplayNameFor(model => model.LabelName) or @Html.DisplayFor(model => model.LabelName) is not generating input tags from which the value of LabelName can be 'collected' by submission of the form.

You have to have something like this in your form:

<input type="hidden" asp-for="LabelName"  />