Could you please explain for me Why and How EF auto assign FK to reference entity when i insert entities into Database? I got these simple Entities like this:
First one is Catalogue
public class Catalogue
{
public int CatalogueId { get; set; }
public string Name { get; set; }
public ICollection<Page> Pages { get; set; }
}
Second one is Page which reference to Catalogue.
public class Page
{
public int PageId { get; set; }
public string Name { get; set; }
public int CatalogueId { get; set; }
public Catalogue Catalogue { get; set; }
}
The relationship in this case is one to many. So in the code i am using this:
using (var context = new MyDbContext())
{
var catalogue = new Catalogue
{
Name = "catalogue 1"
};
var page = new Page
{
Name = "page 1",
CatalogueId = 0
};
context.Catalogues.Add(catalogue);
context.Pages.Add(page);
context.SaveChanges();
}
The MyDbContext is simple nothing special.
When i run this code i am expecting it will generate an error because CatalogueId = 0 is not valid, but it working fine,.
It is interesting me and hopefully someone can clarify that :).
Thanks in advance
This is how EF work under the hood. The context will go and execute the INSERT and generate the update for the FK value in the table. Later, will populate the tracked entity with the real key value.
You can experiment with unattached entities and will notice that no FK value is updated.
Related
I feel like I'm missing something obvious here; I'm using .Net 5 with Entity Framework Core. The problem is that the foreign key is correct, but the associated navigation property is always empty and has no data. Do I have to do something with the fluent framework, or do something special with my includes?
I have 3 simplified entities and a database context method in this example, the project is much too large to include entirely. In the method, CalendarEvents is a DbSet:
public class CalendarEvent: IJsonSerializable
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
/// <summary>
/// Gets the personnel associated with this event
/// </summary>
public virtual List<SchedulePerson> SchedulePeople { get; set; } = new List<SchedulePerson>();
}
public class SchedulePerson : IJsonSerializable, ICloneable
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public int EmployeeId { get; set; }
public virtual Employee Employee { get; set; }
public virtual CalendarEvent AssociatedCalendarEvent { get; set; }
}
public class Employee : IJsonSerializable
{
[Key]
public int Id { get; set; }
public virtual List<SchedulePerson> AssociatedSchedulePeople { get; set; } = new List<SchedulePerson>();
}
public class DbContext : DbContext
{
public DbSet<CalendarEvent> CalendarEvents { get; set; }
public DbSet<SchedulePerson> SchedulePeople { get; set; }
public DbSet<Employee> Employees { get; set; }
public DbContext(DbContextOptions<VibrationContext> options): base(options)
{
}
public CalendarEvent GetEvent(int calendarEventId)
{
var currentCalEvent = this.CalendarEvents.Where(x => x.Id == calendarEventId);
var dummy1 = currentCalEvent.FirstOrDefault();
var dummy2 = currentCalEvent.Include(calEvent => calEvent.SchedulePeople).ToList();
var dummy3 = currentCalEvent.Include(calEvent => calEvent.SchedulePeople).ThenInclude(people => people.Employee).ToList();
return currentCalEvent.FirstOrDefault();
}
}
In this case Employee is the associated navigation property, and the associated key EmployeeId, is correct. For the moment I've added extra logic that will populate each employee per schedule person separately, manually based on the foreign key EmployeeId, when I get the event, but I'd rather not have to add logic like that each time. If that's something unavoidable then that's fine, but I'd like to do things properly and let Entity Framework Core handle as much as possible.
For additional context:
SchedulePerson -> CalendarEvent is a many-to-one relationship
Employee -> SchedulePerson is a many-to-one relationship
In other words a calendar event can contain many schedule persons, but a schedule person can only be associated with one calendar event.
Employee can be associated with many schedule persons, but each schedule person is only associated with one employee.
There should only be one employee for each real person, but there can be multiple SchedulePersons for each real person.
Thank you for your help and let me know if there is any more information I can provide.
Also if anything else looks bad or wrong in these code snippets please let me know.
Edit, this is what I have to do if I want to get the employees in my request:
private void UpdateEmployeeContents(CalendarEvent calendarEvent)
{
foreach (SchedulePerson person in calendarEvent.SchedulePeople)
{
person.Employee = this.Employees.Where(x => x.Id == person.EmployeeId).FirstOrDefault();
}
}
I am working on an API and when I started adding new data. I received this error. It was working when I manually add the ID every input but now I got this error and after adding some solutions from here its still not working.
Error:
Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: Database operation expected to affect 1 row(s) but actually affected 0 row(s).
Data may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.
Code for insert:
public bool Insert(string UserName, SendInventoryModel sendInventoryModel)
{
using (DatabaseContext context = new DatabaseContext())
{
bool flag = false;
// Create new
InventoryEntity inventoryEntity = new InventoryEntity
{
UserName = sendInventoryModel.UserName,
Item = sendInventoryModel.Item ,
};
context.Table.Add(inventoryEntity);
context.SaveChanges();
// Check
var model = CheckUserNameID(UserName, sendInventoryModel.Item);
var data = context.Table.Find(model.Id);
if (null != data)
{
flag = true;
}
return flag;
}
}
SendInventoryModel:
public class SendSiteMailModel
{
[Required]
public string UserName { get; set; }
[Required]
public string Item{ get; set; }
}
InventoryController:
[HttpPost("{username}")]
[Authorize]
public JObject Post([Required] string UserName, [FromBody] SendInventoryModel sendInventoryModel)
{
ResponseModel x = new ResponseModel();
try
{
InventoryRepository InventoryRepository = new InventoryRepository();
bool isSuccess = InventoryRepository.Insert(UserName, sendInventoryModel);
}
catch (Exception error)
{
// if not successful
}
return Json(x);
}
I already added [DatabaseGenerated(DatabaseGeneratedOption.Identity)] in my InventoryEntity and InventoryModel.
InventoryEntity:
[Key]
DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
InventoryModel:
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
I also added the below code in my DBContext.cs:
public virtual DbSet<OtherTableEntity> Table{ get; set; }
public virtual DbSet<InventoryEntity> Table{ get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<OtherTableEntity>();
modelBuilder.Entity<InventoryEntity>().Property(x => x.Id).ValueGeneratedOnAdd();
base.OnModelCreating(modelBuilder);
}
partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
Add finally my table design: Inventory ID:
(Is Identity) = Yes
Identity Increment = 1
Identity Seed = 1
Note that there is no Primary Key in the Inventory table. And its an old table with existing data. The current database was migrated from membership to identity.
After all the things that I have added the context.SaveChanges(); in the insert method still does not work. Any ideas or suggestion on how to fix this problem?
Note: I've changed the table entity names and models per Asherguru suggestion since its kinda confusing and generic.
Are your TableEntity and Table in database same table names?
Why different names - TableEntity and Table?
Try to add [Table("YourTableNameInDatabase")] in TableEntity class. Then EF can find actual table in database and insert into this table.
[Table("YourTableNameInDatabase")]
public partial class TableEntity
{
public int Id { get; set; }
}
It would be less confusing if you show actual table names with some necessary screenshots.
below is my code
I am trying to pull data from database using entityframework.
EmployeeDataContext class -
namespace _09032020_1.Models
{
public class EmployeeDataContext : DbContext
{
public DbSet<Employee> Employees { get; set; }
}
}
Employee model -
namespace _09032020_1.Models
{
[Table("TbleEmployee")]
public class Employee
{
public int employeeId { get; set; }
public string employeeName { get; set; }
public string employeeCity { get; set; }
public string employeeGender { get; set; }
public int departmentId { get; set; }
}
}
below are the table columns.
here is the controller code
namespace _09032020_1.Controllers
{
public class EmployeeController : Controller
{
public ActionResult Index()
{
EmployeeDataContext employeeDataContext = new EmployeeDataContext();
Employee employee = new Employee();
List<Employee> employees1 = new List<Employee>();
employees1 = employeeDataContext.Employees.ToList();
return View(employees1);
}
}
}
I am not getting data inside employeeDataContext
Please let me know if more info regarding config file requires.
Create the table w data. The first column is primary key and identity.
In an MVC project (you can use another type, also I am showing database first, and you can use another type, right click on the Models folder and add ADO.NET Entity Data Model named EmployeeDataContext. Choose EF Designer from database. New connection, and choose your db. Save connection as EmployeeDataContext and choose your table.
Put this in your code:
using (EmployeeDataContext context = new EmployeeDataContext())
{
var emps = context.Employees.ToList();
}
I got my answer,
I have written wrong table name as model attribute [Table("TbleEmployee")]
My table name is TblEmplyee. So it should be [Table("TblEmployee")]
As I changed this I abled to proceed forward.
I have two SQL tables, User and UserType joined with UserType as a foreign key, with their respective models in ASP. To my understanding, this should be a 1:1 relationship (correct me if I'm wrong). One unique user, set as a type of user (being admin, super admin, user etc).
When I try and retrieve a list of users, it returns a null on the property UserType.
I used Google to get this far, but I'm struggling to get this particular issue fixed.
At one point I got an error stating: "Unable to determine the principal end of an association". To get around that, I included a Required annotation (didn't work) and a ForeignKey annotation (didn't work either) in both models, both simultaneously and separately.
This is what I have so far.
[Table("Users", Schema = "dbo")]
public class Users
{
[Key, ForeignKey("UserType")]
public Guid Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string ContactNumber { get; set; }
public UserType UserType { get; set; }
public string IsActive { get; set; }
}
[Table("UserType", Schema = "dbo")]
public class UserType
{
[Key]
public Guid Id { get; set; }
public string Type { get; set; }
public string Description { get; set; }
public string IsActive { get; set; }
public Users Users { get; set; }
}
I'm using the below LINQ method to retrieve the data:
public PagedTables<Users> GetAllUsers(Pagination pagination)
{
using (var db = new DbContext())
{
var user = new PagedTables<Users>()
{
Data = db.Users.OrderBy(U => U.Id).Skip(pagination.Page).Take(pagination.Limit).ToList(),
Count = db.Users.Count()
};
return user;
}
}
A break point on the users var shows that the property UserType returns null. I would expect the assigned user type to be joined onto the user.
Any help would be appreciated. Thanks
My EF background is database-first but if you are eager loading (i.e. not lazy loading) then are you missing an Include to tell LINQ to go and get the UserType? Something like;
Data = db.Users.OrderBy(U => U.Id).Skip(pagination.Page).Take(pagination.Limit).Include(U => U.UserType).ToList(),
I've got my entity class (which is part of my Entity Framework Code First DbContext) like this:
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public virtual Person Boss { get; set; }
public decimal Piotrus { get; set; }
}
Now I'm trying to update persons boss like this:
using(var db = new DataContext())
{
var employee = db.Persons.Single(p => p.Name = "Kowalski");
employee.Boss = db.Persons.Single(p => p.Name = "Malysz");
db.Entry(employee).State = State.Modified;
db.SaveChanges();
}
While debugging entity seems to be ok. It have right Boss assigned. Even when I tried to get data from current DbContext it looks fine, but in Database property Boss_Id stays still unchanged, while other properties (if were changed) has been modified.
Also everything works okay when I'm creating a person. Assigned boss is stored correctly.
What can cause this problem?
Try commenting out db.Entry(employee).State = State.Modified;