Automapper entity framework foreign key is null

问题

I am trying to update the database using entity framework, I map my entities to viewmodels using automapper, and map it back the same way:

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit([FromJson] MyCVViewModel model)
{
    var userId = User.Identity.GetUserId();
    //find the cv
    CV cv = repository.FindCV(model.CVId);

    //auto mapper mapping
    Mapper.CreateMap<MyCVViewModel, CV>();
    Mapper.CreateMap<MyCompanyViewModel, Company>();
    cv = Mapper.Map<MyCVViewModel, CV>(model, cv);

    //edit
    repository.EditCV(cv);
}

When I map it back, the foreign key CVid inside company entity becomes 0, i think something was lost during the mapping process, how do you map the foreign key?

Here is my view model and entity:

View Model:

public class MyCVViewModel
{
    public int CVId { get; set; }

    [Required]
    [StringLength(100, ErrorMessage = "Title cannot exceed 100 characters.")]
    [Display(Name = "Title")]
    public string Title { get; set; }
    [Required]
    [StringLength(1000, ErrorMessage = "Statment cannot exceed 1000 characters.")]
    [Display(Name = "Statement")]
    public string Statement { get; set; }

    public bool Reference { get; set; }

    public List<MyCompanyViewModel> Companies { get; set; }
}

public class MyCompanyViewModel
{
    [Required]
    [StringLength(100, ErrorMessage = "Company Name cannot exceed 100 characters.")]
    [Display(Name = "Company Name")]
    public string CompanyName { get; set; }
    [Required]
    [StringLength(100, ErrorMessage = "Job Title cannot exceed 100 characters.")]
    [Display(Name = "Job Title")]
    public string JobTitle { get; set; }
    [Required]
    [DataType(DataType.Date)]
    [Display(Name = "Start Date")]
    public DateTime StartDate { get; set; }
    [Required]
    [DataType(DataType.Date)]
    [Display(Name = "End Date")]
    public DateTime EndDate { get; set; }
    [Required]
    [StringLength(1000, ErrorMessage = "Job Description cannot exceed 1000 characters.")]
    [Display(Name = "Job Description")]
    public string Description { get; set; }
}

Entity:

public class CV
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int CVId { get; set; }
    public string Title { get; set; }
    public string Statement { get; set; }
    public bool Reference { get; set; }

    public virtual ICollection<Company> Companies { get; set; }
}

public class Company
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int CompanyId { get; set; }

    public string CompanyName { get; set; }
    public string JobTitle { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
    public string Description { get; set; }

    public virtual CV CV { get; set; }
    public int CVId { get; set; }
}

and this is the error message when I try to update:

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value.

I see where the problem is, but don't know how to tell automapper to retain foreign key value

回答1:

MyCompanyViewModel class does not contain a definition of CVId property, so by default Automapper does not know where he should take a value for injecting into Company's CVId property. Just define it:

public class MyCompanyViewModel
{
    public int CVId { get; set; }
    // Other properties
}

Then for each CompanyViewModel add corresponding hidden input field into the view:

@for (int i = 0; i < Model.Companies.Count; i++)
{

    // ...

    @Html.HiddenFor(m => Model.Companies[i].CVId)

    // ...

}

and you are good to go!

来源：https://stackoverflow.com/questions/28955542/automapper-entity-framework-foreign-key-is-null

标签

asp.net-mvc

entity-framework

automapper