So I try to create some ASP.NET project with EF Core.
I want to set propert of one entity as primary key and foreign key to another entity. The relationship is 0..1 - 1. I use DataAnnotations:
public class OfficeAssignment
{
[Key, ForeignKey("InstructorID")]
public int InstructorID { get; set; }
public Instructor Instructor { get; set; }
public string Location { get; set; }
}
But I keep getting column InstructorID as PK and InstructorID1 as FK... Any ideas, why EF behaves like that and how can I achieve my goal?
You should follow convention over configuration as much as you can. An OfficeAssignment entity should have an OfficeAssignmentId PK, like this:
public class OfficeAssignment
{
public int OfficeAssignmentId { get; set; }
//Notice that Id does not have an uppercase D
public int InstructorId { get; set; }
public string Location { get; set; }
public Instructor Instructor { get; set; }
}
However, if you don't want to follow normal conventions, the name of the property that goes in the ForeignKey attribute is the opposite of where it's declared:
public class OfficeAssignment
{
[Key, ForeignKey("Instructor")]
public int InstructorId { get; set; }
public string Location { get; set; }
public Instructor Instructor { get; set; }
}
And, if you want to keep it compile-time safe:
public class OfficeAssignment
{
[Key, ForeignKey(nameof(Instructor))]
public int InstructorId { get; set; }
public string Location { get; set; }
public Instructor Instructor { get; set; }
}
It's enough to set primary key attribute([Key]) in the OfficeAssignment class and in Instructor class we need to set such attribute:
[InverseProperty("Instructor")]
on collection of CourseAssignments. That will work as desired.
Related
I'm trying to add some entities using EntityFramework.
I need the same model as in image
I created two classes:
public class PriceOfDish
{
[Key]
public virtual List<Dish> Dish_ID { get; set; }
[Key]
public DateTime DateTime { get; set; }
public decimal Price { get; set; }
}
public class Dish
{
[Key]
public int Dish_ID { get; set; }
public string DishName { get; set; }
public string Description { get; set; }
public virtual FoodCategory FoodCategory_ID { get; set; }
public virtual Feature Feature_ID { get; set; }
public virtual ICollection<OrderedDishes> Orders { get; set; }
}
Using FluentAPI trying to set primary keys:
builder.Entity<PriceOfDish>()
.HasKey(t => new {t.Dish_ID, t.DateTime});
During updating DB i get error message: "The property 'Dish_ID' cannot be used as a key property on the entity 'testFOef.PriceOfDish' because the property type is not a valid key type. Only scalar types, string and byte[] are supported key types.".
But why? Can you explain this to me? Thanks for any help
Like the error say you are using a List<Dish> as a type for your primary key. You must use an scalar type (value type) as usual or byte[].
For you, the solution is to create a proprerty Dish_ID with int type.
public class PriceOfDish
{
[Key]
public int Dish_ID { get; set; }
[Key]
public DateTime DateTime { get; set; }
[ForeignKey("Dish_Id")]
public virtual Dish Dish { get; set; }
public decimal Price { get; set; }
}
you're trying to set a List<Dish> Dish_ID as a key of a table.
But this is not supported. It doesn't make much sense either. list of Dishes that will have a single Price? I think you want to put int Dish_ID there
I am trying to create a composite key using two fields when using code first to existing fields in a table in a db;
[Key,Column("driverId", Order=0)]
[JsonProperty(PropertyName="driverid")]
public override int ID { get; set; }
[Key,Column("type", Order=1)]
[JsonProperty(PropertyName="typeid")]
public int Type { get; set; }
Now when I try to run a new migration i get the following error;
The number of properties in the Dependent and Principal Roles in a relationship constraint must be identical.
DriversToVehicle_Driver_Target_DriversToVehicle_Driver_Source: : The number of properties in the Dependent and Principal Roles in a relationship constraint must be identical.
The DriversToVehicle table is as follows;
public partial class DriversToVehicle
{
[Column("id"), Key]
public int ID { get; set; }
[Column("driverid")]
public int DriverID { get; set; }
[ForeignKey("DriverID")]
public Driver Driver { get; set; }
[Column("vehicleid")]
public int VehicleID { get; set; }
[ForeignKey("VehicleID")]
public Vehicle Vehicle { get; set; }
}
Extending this question, originally a single key on the ID, i.e.
[Column("driverId")]
[JsonProperty(PropertyName="driverid")]
public override int ID { get; set; }
Now moving forward, how will this effect the other entities linking to it (by this i mean code first in the classes)? will ef automatically sort this out? or do I now need to have both keys in other entities when linking to this class?
e.g. as before I would have had
public virtual Driver myDriver;
Obviously now instead of linking on the ID alone it needs to be linked with the Type as well.
Thanks in advance.
EDIT FOR ANSWER
Ok, I extracted the Type out to a seperate class. The main issue is now How do i mark the foreign key as also being a composite key?
I have the following classes
public partial class DriverType
{
[Column("Id")]
[JsonProperty(PropertyName = "drivertypeid")]
public override int ID { get; set; }
[JsonProperty(PropertyName = "drivertype")]
public string Name { get; set; }
}
Then in the Driver I have the following (reduced for brevity);
public partial class Driver : AuditableEntity<int>
{
[Key,Column("driverId", Order=0)]
[JsonProperty(PropertyName="driverid")]
public override int ID { get; set; }
[Key,Column("type", Order=1)]
[ForeignKey("DriverType")]
[JsonProperty(PropertyName="drivertypeid")]
public int DriverTypeId { get; set; }
public DriverType DriverType { get; set; }
How do I then add it to the DriverToVehicle class please? So far I have
public partial class DriversToVehicle
{
[Column("id"), Key]
public int ID { get; set; }
[Column("driverid", Order=0), ForeignKey("Driver")]
public int DriverID { get; set; }
public Driver Driver { get; set; }
[Column("type", Order = 1), ForeignKey("Driver")]
public int DriverTypeId { get; set; }
[ForeignKey("DriverTypeId")]
public DriverType DriverType { get; set; }
}
This doesnt look right to me though?
Since your Drivers table's Primary Key is now (DriverId, Type), you can no longer reference your drivers by DriverId alone - you must reference them by both DriverId and Type. Therefore, your DriversToVehicle table needs to look something like this:
public partial class DriversToVehicle
{
[Column("id"), Key]
public int ID { get; set; }
[Column("driverid")]
public int DriverID { get; set; }
[ForeignKey("DriverID")]
public Driver Driver { get; set; }
[Column("DriverType")]
public int DriverType { get; set; }
[ForeignKey("type")]
public int DriverType { get; set; }
[Column("vehicleid")]
public int VehicleID { get; set; }
[ForeignKey("VehicleID")]
public Vehicle Vehicle { get; set; }
}
However, as #hopeless states above, you may not need to model this join table if you correctly model your Driver and Vehicle types correctly.
HTH.
So i am trying to create a table with a foreign key, but it always says that it cannot find the foreign key. heres the code:
public class Tecnologies
{
[Key]
public int TecId { get; set; }
[Required]
public String Name { get; set; }
}
this one works, then i try to create this one:
public class UserTecnologies
{
[Key]
public int UserTecId { get; set; }
[ForeignKey("Id")]
public UserProfile User { get; set; }
[ForeignKey("TecId")]
public virtual Tecnologies Tecnology { get; set; }
[Required]
public int Rating { get; set; }
}
and it gives me the error :
The ForeignKeyAttribute on property 'Tecnology' on type 'ESW_CloddOffice.Models.UserTecnologies' is not valid. The foreign key name 'TecId' was not found on the dependent type 'ESW_CloddOffice.Models.UserTecnologies'. The Name value should be a comma separated list of foreign key property names.
The names are correct, what am i missing ?
Okay, i found what i was doing wrong. Heres the correct code:
public class UserTecnologies
{
[Key]
public int UserTecId { get; set; }
[ForeignKey("UserProfile")]
public virtual int UserProfileId { get; set; }
[ForeignKey("Tecnology")]
public virtual int TecnologyId { get; set; }
public virtual Tecnologies Tecnology { get; set; }
public virtual UserProfile UserProfile { get; set; }
[Required]
public int Rating { get; set; }
}
Was creating the foreign key the wrong way .
The ForeignKey attribute requires that an actual property on the entity match the name you pass in. It doesn't just tell EF what to call the key at the database level.
You either need to actually add a TecId property:
public int TecId { get; set; }
Or use fluent configuration, instead:
modelBuilder.Entity<UserTechnologies>()
.HasRequired(c => c.Technology)
.WithMany()
.Map(m => m.MapKey("TecId"));
I've got the following domain models (pseudo):
public class Camera {
public int Id { get; set; }
}
public class Display {
public int Id { get; set; }
}
public class SetupGroup {
public int Id { get; set; }
public virtual ICollection<CameraDisplayMap> Mappings { get; set; }
}
public class CameraDisplayMap {
public int Id { get; set; }
public Camera Camera { get; set; }
public Display Display { get; set; }
}
which should get mapped the following way:
[Cameras]
Id (primary key)
[Displays]
Id (primary key)
[SetupGroup]
Id (primary key)
[CameraDisplayMap]
Id (foreign key to [SetupGroup]
Camera (foreign key to [Cameras])
Display (foreign key to [Display])
I am aware the data model is not ideal, but it's a requirement in order to support one of our legacy applications which handled most mapping etc. with application logic.
Currently, I'm unable to configure this mapping with the given relationship instructions from EF Code First Fluent Configuration API, or at least I'm not sure how to do it. I tried mapping beginning from SetupGroup using WithMany, but here I can't declare that Camera and Display should be mapped on the CameraDisplayMap. Starting from CameraDisplayMap, I'm unable to declare the Id as being a foreign key to SetupGroup. Am I missing something?
CameraDisplayMap Class should be like following.
public class CameraDisplayMap {
public int Id { get; set; } //primary key
public int? SetupGroupId { get; set; } //foreign key to [SetupGroup]
public int? CameraId { get; set; } //foreign key to [Camera]
public int? DisplayId Displays { get; set; } //foreign key to [Display]
public virtual SetupGroup SetupGroups { get; set; }
public virtual Camera Cameras { get; set; }
public virtual Display Displays { get; set; }
}
So i am working with entity code firest and i have a user class that looks like this:
public class User
{
[Key]
public string Username { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime LastModified { get; set; }
}
I am trying to make a "friends table" and no matter what i come up with I get an error on the db creation. This is what I Currently have in the Friends Class:
public class Friend
{
[Key, ForeignKey("User")]
public virtual User MyUser { get; set; }
[Key,ForeignKey("User")]
public virtual User MyFriend { get; set; }
public bool IsAccepted { get; set; }
}
this is the error i get:
The ForeignKeyAttribute on property 'MyUser' on type 'Core.Model.Friend' is not valid. The foreign key name 'User' was not found on the dependent type 'Core.Model.Friend'. The Name value should be a comma separated list of foreign key property names.
What am I missing?
You need to use the Column attribute. Normally I would use something like this:
public class Friend
{
[Key]
[Column(Order = 0)]
public int MyUserId { get; set; }
[Key]
[Column(Order = 1)]
public int MyFriendId { get; set; }
[ForeignKey("MyUserId")]
public virtual User MyUser { get; set; }
[ForeignKey("FriendId")]
public virtual User MyFriend { get; set; }
public bool IsAccepted { get; set; }
}
I'm not sure what would happen if you map the Column attribute directly to the navigation property. You can try it if you like and see what happens.. but the above generally works for me.
Alternatively, if you change to use fluent mapping, you can do something like this:
HasKey(u => new { u.MyUserId , u.MyFriendId });