Automapper实体框架外键为空

我正在尝试使用实体框架更新数据库，我使用自动映射器将实体映射到视图模型，并以相同的方式将其映射回来：

[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);
}

当我映射回来时，公司实体内的外键CVid变成0，我认为在映射过程中丢失了一些东西，你如何映射外键？

这是我的视图模型和实体：

查看型号：

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; }
}

这是我尝试更新时的错误消息：

操作失败：无法更改关系，因为一个或多个外键属性不可为空。当关系发生更改时，相关的外键属性将设置为空值。

我明白问题出在哪里，但不知道如何告诉自动映射器保留外键值

MyCompanyViewModel类不包含定义CVId财产，所以默认情况下 Automapper 不知道他应该在哪里取一个值来注入Company's CVId财产。只需定义它：

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

然后对于每个CompanyViewModel将相应的隐藏输入字段添加到视图中：

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

    // ...

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

    // ...

}

一切顺利！