我的加载的孩子是丢失当使用自动器

我正在用Automapper映射我的实体对象，正如您将在下面的评论中看到的，我的组集合在映射后丢失了。

 public partial class WebUser
{
    public WebUser()
    {
        this.WebUserGroups = new HashSet<WebUserGroup>();
    }
    public int UserKey { get; set; }
    //stuff
    public virtual ICollection<WebUserGroup> WebUserGroups { get; set; }
}
public void Edit(WebUser user)
    {
        //Has collection of WebUserGroups populated
        var userToBeEdited = GetUserBy(user.UserKey);
        var updatedWebUser = Mapper.Map(user, userToBeEdited);
        //Lost after mapping
        _context.Entry(updatedWebUser).State = EntityState.Modified;
        _context.SaveChanges();
    }
public WebUser GetUserBy(int userKey)
{
    return (from webUser in _context.WebUsers
        join webUserGroup in _context.WebUserGroups on webUser.UserKey equals webUserGroup.UserKey
        select webUser).FirstOrDefault();
}
Mapper.CreateMap<WebUser, WebUser>()
            .ForSourceMember(dest => dest.UserKey, src => src.Ignore())
            .ForSourceMember(dest => dest.WebUserGroups, src => src.Ignore());

有什么建议吗?

Mapper.CreateMap<WebUser, WebUser>()
    .ForMember(dest => dest.UserKey, opt => opt.Ignore())
    .ForMember(dest => dest.WebUserGroups, opt => opt.Ignore());