Automapper not working with .MapFrom on ternary and calculated value with Net Core 2.2

Question

I ma using;

AutoMapper.Extensions.Microsoft.DependencyInjection 6.0.0

in a web api project trunning net core 2.2

when mapping my DTO object I use Automapper to map a few fields;

public class AutoMapperProfile : AutoMapper.Profile
{
    public AutoMapperProfile()
    {     
        CreateMap<ReviewPostInputModel, Review>()
            .ForMember(x => x.ReceiveThirdPartyUpdates, opt => opt.MapFrom(src => src.ReceiveThirdPartyUpdates ? (DateTime?)DateTime.UtcNow : null))
            .ForMember(x => x.ReceiveUpdates, opt => opt.MapFrom(src => src.ReceiveUpdates ? (DateTime?)DateTime.UtcNow : null))
            .ForMember(x => x.AverageScore, opt => opt.MapFrom(src => (decimal)Math.Round((src.Courtsey + src.Reliability + src.Tidiness + src.Workmanship) / 4, 2)));
        // ...
    }
}

Where;

using System;
using System.Collections.Generic;
using System.Text;

public class Review 
{
    // ...

    public decimal Reliability { get; set; }
    public decimal Tidiness { get; set; }
    public decimal Courtsey { get; set; }
    public decimal Workmanship { get; set; }

    public decimal AverageScore { get; set; }
    public DateTime? ReceiveUpdates { get; set; }
    public DateTime? ReceiveThirdPartyUpdates { get; set; }
} 

However, when I try to map using;

var review = _mapper.Map<Review>(model);

All standard members are mapped bar my ForMember listed above, where the DateTimes are set to a new instance of DateTime and Averagescore is set to 0.

For completness I DI the mapper into my controller as follows;

private readonly IMapper _mapper;

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

I configure Automapper in my StartUp.cs as follows;

services.AddAutoMapper();

I have also tried adding a test to the controller to confirm that the values from the input are not the issue (completed after the map and can confirm that this value is correctly updated);

review.AverageScore = (decimal)Math.Round((model.Courtsey + model.Reliability + model.Tidiness + model.Workmanship) / 4, 2);

Does anyone have any ideas why this is occurring?

Answer 1

You need to use "ResolveUsing" and not "MapFrom"

public class AutoMapperProfile : AutoMapper.Profile
{
    public AutoMapperProfile()
    {     
        CreateMap<ReviewPostInputModel, Review>()
            .ForMember(x => x.ReceiveThirdPartyUpdates, opt => opt.ResolveUsing(src => src.ReceiveThirdPartyUpdates ? (DateTime?)DateTime.UtcNow : null))
            .ForMember(x => x.ReceiveUpdates, opt => opt.ResolveUsing(src => src.ReceiveUpdates ? (DateTime?)DateTime.UtcNow : null))
            .ForMember(x => x.AverageScore, opt => opt.ResolveUsing(src => (decimal)Math.Round((src.Courtsey + src.Reliability + src.Tidiness + src.Workmanship) / 4, 2)));
        // ...
    }
}

You can look on this answer: AutoMapper: What is the difference between MapFrom and ResolveUsing?

We had a problem in the past when adding auto mapper from "ConfigureServices" and may be it is the same for you. You can try to put this:

AutoMapperConfiguration.Init();

in Startup function and add this class:

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using AutoMapper;

namespace yournamespace.ViewModels.Mappings
{
    public static class AutoMapperConfiguration
    {
        public static void Init()
        {
            Mapper.Initialize(cfg =>
            {
                cfg.CreateMap<ReviewPostInputModel, Review>()
                .ForMember(x => x.ReceiveThirdPartyUpdates, opt => opt.MapFrom(src => src.ReceiveThirdPartyUpdates ? (DateTime?)DateTime.UtcNow : null))
                .ForMember(x => x.ReceiveUpdates, opt => opt.MapFrom(src => src.ReceiveUpdates ? (DateTime?)DateTime.UtcNow : null))
                .ForMember(x => x.AverageScore, opt => opt.MapFrom(src => (decimal)Math.Round((src.Courtsey + src.Reliability + src.Tidiness + src.Workmanship) / 4, 2)));
            });
        }
    }
}

Answer 2

After some investigation, I think I have reproduced your problem. I created a basic ASP.NET Core 2.2 website, installed AutoMapper.Extensions.Microsoft.DependencyInjection 6.0.0, created a Review class that matches yours and a best guess of what ReviewPostInputModel class looks like based on your mapping definition. I then added your mapping profile class AutoMapperProfile into the project, and configured start up like so:

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.AddAutoMapper();
    services.AddMvc...
}

I then "hacked" the default generated HomeController like so to test the mapping:

 public class HomeController : Controller
    {
        private IMapper _mapper;

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

        public IActionResult Index()
        {
            var input = new ReviewPostInputModel();
            input.ReceiveThirdPartyUpdates = true;
            input.Tidiness = 3;
            input.Reliability = 2;
            input.NotDefinedOnProfile = "sss";

            var output = _mapper.Map<Review>(input);

            // Lazy test to avoid changing model.
            throw new Exception($"{output.ReceiveThirdPartyUpdates} - {output.AverageScore} - {output.NotDefinedOnProfile}");

            return View();
        }
...

Now this worked for me, as in the Exception message I received was 11/04/2019 2:56:31 PM - 1.25 - sss.

I then created another assembly and moved the AutoMapperProfile class into it. I then re-run the test, but got the following error:

AutoMapper.AutoMapperConfigurationException: Unmapped members were found. Review the types and members below. Add a custom mapping expression, ignore, add a custom resolver, or modify the >source/destination type

For no matching constructor, add a no-arg ctor, add optional arguments, or map all of ?the constructor parameters

AutoMapper created this type map for you, but your types cannot be mapped using the >current configuration. ReviewPostInputModel -> Review (Destination member list) ReviewPostInputModel -> Review (Destination member list)

Unmapped properties: AverageScore ReceiveUpdates NotDefinedOnProfile

This makes sense, since the services.AddAutoMapper(); method only searches the currently assembly for profiles.

So I then changed to configuration to: services.AddAutoMapper(cfg => cfg.ValidateInlineMaps = false); to turn off the error, and re-run the test.

New Output: 1/01/0001 12:00:00 AM - 0 - sss

So this leads me to believe that AutoMapper can't find your Profile class, in which case, you can manually configure it using:

 services.AddAutoMapper(cfg =>
 {
    cfg.AddProfile<AutoMapperProfile>();
 });

or manually define the assemblies to search by using one of the other overloads e.g.:

services.AddAutoMapper(param System.Reflection.Assembly[] assemblies);

If this is not your problem, no matter because my time spent reproducing this question has cured my insomnia.