Mapping DTO back to model with AutoMapper

Question

I have a Fixture model :

public partial class Fixture
{
    public int FixtureId { get; set; }
    public string Season { get; set; }
    public byte Week { get; set; }

    //foreign key
    public int AwayTeamId { get; set; }
    //navigation properties
    public virtual Team AwayTeam { get; set; }

    //foreign key
    public int HomeTeamId { get; set; }
    //navigation properties
    public virtual Team HomeTeam { get; set; }

    public byte? AwayTeamScore { get; set; }
    public byte? HomeTeamScore { get; set; }
}

And a Fixture DTO :

public class FixtureDTO
{
    public int Id { get; set; }
    public string Season { get; set; }
    public byte Week { get; set; }
    public string AwayTeamName { get; set; }
    public string HomeTeamName { get; set; }
    public byte? AwayTeamScore { get; set; }
    public byte? HomeTeamScore { get; set; }
}

I am using AutoMapper for the mapping and this is my first attempt using it. Here is my mapping :

CreateMap<Fixture, FixtureDTO>()
            .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.FixtureId))
            .ForMember(dest => dest.AwayTeamName, opt => opt.MapFrom(src => src.AwayTeam.TeamName))
            .ForMember(dest => dest.HomeTeamName, opt => opt.MapFrom(src => src.HomeTeam.TeamName));
        CreateMap<FixtureDTO, Fixture>();

It works fine in taking the Fixture and mapping it to the FixtureDTO which I use to display the data. But when I want to update the data and pass the FixtureDTO back to map it back to Fixture I get an error.

public HttpResponseMessage PutFixture(int id, FixtureDTO fixture)
    {
        if (ModelState.IsValid && id == fixture.Id)
        {
            //do mapping manually here?

            var updated = _repository.UpdateFixture(Mapper.Map<Fixture>(fixture));
            return Request.CreateResponse(updated ? HttpStatusCode.OK : HttpStatusCode.NotFound);
        }
        return Request.CreateResponse(HttpStatusCode.BadRequest);
    }

This is the error I get :

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

Can anybody help with this?

EDIT : Reverse mapping :

CreateMap<Fixture, FixtureDTO>()
            .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.FixtureId))
            .ForMember(dest => dest.AwayTeamName, opt => opt.MapFrom(src => src.AwayTeam.TeamName))
            .ForMember(dest => dest.HomeTeamName, opt => opt.MapFrom(src => src.HomeTeam.TeamName));
        CreateMap<FixtureDTO, Fixture>()
            .ForMember(dest => dest.FixtureId, opt => opt.MapFrom(src => src.Id))
            .ForMember(dest => dest.AwayTeam.TeamName, opt => opt.MapFrom(src => src.AwayTeamName))
            .ForMember(dest => dest.HomeTeam.TeamName, opt => opt.MapFrom(src => src.HomeTeamName));

Answer 1

Generally that exception is thrown by EF when it detects one of the following:

Opimistic Concurrency Violation: This usually occurs when the entity you are trying to edit was modified else where during the time you loaded, edited and saved it. (see: Entity Framework: "Store update, insert, or delete statement affected an unexpected number of rows (0).")

An Incorrectly set ID: No ID set for Pks or FKs. I've also seen an exception like this when I mistakenly set an Entity's FK to a value and set the associated object to an object with a different ID.

Most likely this exception is being thrown because of some code in your repository. If you post the code in your repository we might get a better idea of what is causing the exception.

Answer 2

First, you need to create reverse mapping from DTO to entity (provide custom member mappings, if needed):

Mapper.CreateMap<FixtureDTO, Fixture>();

And second - retrieve, map, and update existing entity

if (ModelState.IsValid && id == fixture.Id)
{
    Fixture entity = _repository.FindById(fixture.Id);
    Mapper.Map(fixture, entity); // Use this mapping method!
    var updated = _repository.UpdateFixture(entity);
    // etc
} 

Answer 3

Extension to @lazyberezovsky's answer:

This is an (untested) example of the reverse mapping you might require:

CreateMap<FixtureDTO, Fixture>()
        .ForMember(dest => dest.FixtureId,
                   opt => opt.MapFrom(src => src.Id))
        .ForMember(dest => dest.AwayTeam,
                   opt => opt.MapFrom(src => new Team
                                                 {
                                                     TeamName = src.AwayTeamName
                                                 }))
        .ForMember(dest => dest.HomeTeam,
                   opt => opt.MapFrom(src => new Team
                                                 {
                                                     TeamName = src.HomeTeamName
                                                 }));

I've used this format in the past and its worked fine, but alternatively you could also create specific mappings for team. Eg:

CreateMap<string, Team>()....

Also, I presume you are doing it, but assert that your configuration is valid. Eg:

[Test]
public void AutoMapper_Configuration_IsValid()
{
    Mapper.Initialize(m => m.AddProfile<MyProfile>());
    Mapper.AssertConfigurationIsValid();
}