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How can I specify to add item to the database without also adding the foreign key?

I have the following Models:
public interface Item
{
public int Id { get; set; }
}
public class ComponentOwner : Item
{
public int Id { get; set; }
public Component Component { get; set; }
public AppUser? User { get; set; }
public DateTime ModifiedDate { get; set; }
public AppUser? UpdatedBy { get; set; }
}
public class AppUser : IdentityUser
{
public string FirstName { get; set; } = "";
public string LastName { get; set; } = "";
}
and the following async Task that saves the item to the database:
private async Task<Item> SaveItem(Item item)
{
Item updatedItem = null;
using var context = _dbContextFactory.CreateDbContext();
try
{
if (item.Id == 0)
{
context.Add(item);
await context.SaveChangesAsync();
}
When I Save a new ComponentOwner, context.Add(Item) adds the item, but also tries to add a new 'AppUser' at the same time. This causes issues because the AppUser is already created.
Is there a way that I can specify to add the ComponentOwner but not the AppUser?
as soon as 'Context.Add(item)' is hit, it wants to add an AppUser as well as the Component. I only want it to add the ComponentOwner however..

EF Core relies on tracking to determine what to do with entities. In this case it seems that item.User is not tracked, so EF tries to add it. There are multiple possible solution to this. To name a few:
If you are sure that user exists, you can just attach the entity:
if(item.User is not null)
context.Users.Attach(item.User); // or just context.Attach(item.User);
Fetch user from database and assign it to the root entity:
if (item.User is not null)
{
var user = context.Users.FirstOrDefault(u => u.Id == item.User.Id); // TODO: handle null
item.User = user;
}
Use Find:
Finds an entity with the given primary key values. If an entity with the given primary key values is being tracked by the context, then it is returned immediately without making a request to the database. Otherwise, a query is made to the database for an entity with the given primary key values and this entity, if found, is attached to the context and returned. If no entity is found, then null is returned.
if (item.User is not null)
{
var user = context.Users.Find(item.User.Id); // TODO: handle null
item.User = user;
}

How to map users identity and Auditable properties in view model

This is my view model.
public class ProductViewModel
{
public Guid Id { get; set; }
public string Code { get; set; }
public string Name { get; set; }
public bool IsAvailable { get; set; }
}
When form is posted from client the form is submitted to this Controller
public async Task<IHttpActionResult> AddProduct(ProductViewModel productViewModel)
{
await ServiceInstances.PostAsync("product/add", productViewModel);
return Ok();
}
Then this controller submit the form to the API controller
Which is on my separate Project.
[HttpPost]
[Route("add")]
public IHttpActionResult AddProduct(ProductViewModel model)
{
_productService.AddProduct(model.UserServiceDetails());
return Ok();
}
Extension UserServiceDetails Where i get the Login User Info
public static UserServiceDetailModel<T> UserServiceDetails<T>(this T model)
{
var serviceRequestModel = new ServiceRequestModel<T>()
{
Model = model,
LoginInfo = HttpContext.Current.User.Identity.GetUserLoginInfo();
};
}
AddProductService:
public void AddProduct(UserServiceDetailModel<ProductViewModel> serviceRequestModel)
{
var repo = _genericUnitOfWork.GetRepository<Product, Guid>();
var mapped = _mapper.Map<ProductViewModel, Product>(serviceRequestModel.Model);
mapped.Id = Guid.NewGuid();
mapped.CreatedDate = GeneralService.CurrentDate();
mapped.CreatedById = serviceRequestModel.LoginInfo.UserId;
repo.Add(mapped);
_genericUnitOfWork.SaveChanges();
}
Now my question is Is there any way to assign the value to this field CreatedDate and CreatedById before posting it to service?
Reduce these logic to mapper:
mapped.CreatedDate = GeneralService.CurrentDate();
mapped.CreatedById = serviceRequestModel.LoginInfo.UserId;
Or is there any way that those field gets mapped to Product when
var mapped = _mapper.Map<ProductViewModel, Product>(serviceRequestModel.Model);
Sometime i may have the List<T> on view-model and there i have to add this field using the loop.
So this same mapping may get repeated over and over on Add Method Or Update.
In some entity i have to assign the ModifiedDate and ModifiedById also.
My Mapper Configuration:
public class ProductMapper : Profile
{
public ProductMapper()
{
CreateMap<ProductViewModel, Product>();
}
}
I cannot add the Enitity as IAuditableEntity and Overrride in ApplicationDbContext because my DbContext is in separate Project and i donot have access to Identity there.

Based on class that has no key defined mvc5

I try to add view from this controller . I only need this view to show data not for insert or update or delete
public ActionResult Index()
{
var CartObj = ShoppingCart.GetCart(this.HttpContext);
var classshop = new New
{
CartItems = CartObj.GetCartItems(),
CartTotal = CartObj.GetSum()
};
return View(classshop);
}
namespace MusicStore.Models
{
public class ShoppingCart
{
MusicStoreEntities dbo = new MusicStoreEntities();
string ShoppingCartID { get; set; }
public const string CartSessionKey = "CartId";
public static ShoppingCart GetCart(HttpContextBase Context)
{
var cart = new ShoppingCart();
cart.ShoppingCartID = cart.GetCardId(Context);
return cart;
}
public static ShoppingCart GetCart(Controller controller)
{
return GetCart(controller.HttpContext);
}
public List<Cart> GetCartItems()
{
return dbo.Carts.Where(a => a.CartId == ShoppingCartID).ToList();
}
public decimal? GetSum()
{
decimal? Sum = (from items in dbo.Carts
where items.CartId == ShoppingCartID
select (int)items.Count * items.album.Price).Sum();
return Sum ?? decimal.Zero;
}
}
}
and then I got this error:
there was an error running the selected code generator:
'unable to retrieve metadata for 'Musicstore.Model.new'
one or more validation error were detected during model generation
musicstore,models.New :entity type'New' has no key defined .
define the key of entityType
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace MusicStore.Models
{
public class New
{
public List<Cart> CartItems { get; set; }
public decimal? CartTotal { get; set; }
}
}

There are two options here. First, if this class is mapped to a table in your database, every model in entity framework requires a primary key. Add this into your model:
[Key]
public int Id { get; set; }
This creates a new property called Id and the [Key] attribute makes it a primary key. Technically you don't need the attribute as EF will pick up Id property and use it as a key, but I prefer to be explicit.
Alternatively, if you don't want this class to be a table in your database, add the NotMapped attribute to the class like this:
[NotMapped]
public class New
{
public List<Cart> CartItems { get; set; }
public decimal? CartTotal { get; set; }
}

I know this is old, but I just ran across this issue.
What happen is when I created a class, CreateEmployeeViewModel, inside the Models folder Visual Studio "smartly" put a line in my DB Context class
public System.Data.Entity.DbSet<eManager.Web.Models.CreateEmployeeViewModel>
CreateEmployeeViewModels { get; set; }
So a table was created on the next update-migration. Removing this line removed the requirement for a key field.
Note: You may also have to add the line AutomaticMigrationDataLossAllowed = true; to your DBMigrationConfiguration Class if the table was created.

Converting a string into a List and then using Entity Framework to insert into Database

I am converting a string into a list and then trying to use entity framework to insert it into a DB. The issue that I am having is that I don't know how to save the changes to the DB.
This is the code that I am trying to use and is where the string is converted to a list:
if (intCounter == 0)
{
return JsonConvert.DeserializeObject<List<foo>>(jsonString).Cast<T>().ToList();
}
Then in a seperate class below.
ConvertJson.Convert<CouncilEvent>(strResponseJSONContent, intCounter);
The Entity Framework Model that I am trying to use for the list.
namespace foo.Models
{
public partial class foo
{
public foo()
{
this.EventDates = new List<EventDate>();
}
public System.Guid foo_PK { get; set; }
public string EntityID { get; set; }
public string Address1 { get; set; }
public string Address2 { get; set; }
public string Address3 { get; set; }
public bool Adult { get; set; }
}
}
The class foo contains properties that match those in the string.
It is this foo that I am then trying to insert into the DB. foo is also part of my Entity Framework model.
I have never used a list in this situation before and I thought it would just be a matter of using db.SaveChanges() but that doesn't seem to work. Where would I place the necessary lines of code such as using (db = new contextFoo) and db.SaveChanges(). Also do I need to add the items? I haven't because I thought I was already adding them to the class and therefore didn't need to do this manually?

db.SaveChanges() will only 'update' your database to what was changed. So, you need to add something to the database, and then call SaveChanges() for it to work.

You can loop the list to add the objects to the context, then call SaveChanges()...
var councilEvents = ConvertJson.Convert<CouncilEvent>(strResponseJSONContent, intCounter);
using (var db = new contextFoo())
{
foreach (var councilEvent in councilEvents)
{
db.CouncilEvents.Add(councilEvent);
}
db.SaveChanges();
}

MVC3 EF4 duplicates foreign key object on save

I'm using MVC3 with EF4 code-first. I have the following model:
public class Order {
public int ID { get; set; }
[Required]
public float Price { get; set; }
[Required]
public int PayMethodId { get; set; }
public PayMethod PayMethod { get; set; }
public int? SpecificEventId { get; set; }
public SpecificEvent SpecificEvent { get; set; }
public int? SeasonalTicketId { get; set; }
public SeasonalTicket SeasonalTicket { get; set; }
}
When I try to save an Order object with specificEventId = 2 and specificEvent = X, a new SpecificEvent object is created in the DB, even though there's already a specific event X with ID 2 in the DB. When i try with specificEventId = 2 and specificEvent = null I get a data validation error.
What am I doing wrong? I want SpecificEvent and SeasonalTicket to be nullable, and I don't want EF4 to create a new instance of these objects in the DB whenever I save 'Order'.
Update
This is my code for saving Order in the DB:
public void SaveOrder(Order order)
{
Order fromDb = null;
// If editing an existing object.
if ((fromDb = GetOrder(order.ID)) != null)
{
db = new TicketsDbContext();
db.Entry(order).State = System.Data.EntityState.Modified;
db.SaveChanges();
}
// If adding a new object.
else
{
db.orders.Add(order);
db.SaveChanges();
}
}
When I save, I do reach the else clause.

The real question is, where did you get the instance of X from? It appears as though EF has no knowledge of this instance. You either need to fetch the already existing SpecificEvent through EF and use the proxy it returns to set your navigation property, or else tell EF to "attach" X, so that it knows what your intent is. As far as EF knows, it appears, you are trying to send it a new instance with a conflicting Id, so it is properly issuing the error.