I'm using Entity Framework 5.0 Code First;
public class Entity
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public string EntityId { get; set;}
public int FirstColumn { get; set;}
public int SecondColumn { get; set;}
}
I want to make the combination between FirstColumn and SecondColumn as unique.
Example:
Id FirstColumn SecondColumn
1 1 1 = OK
2 2 1 = OK
3 3 3 = OK
5 3 1 = THIS OK
4 3 3 = GRRRRR! HERE ERROR
Is there anyway to do that?
With Entity Framework 6.1, you can now do this:
[Index("IX_FirstAndSecond", 1, IsUnique = true)]
public int FirstColumn { get; set; }
[Index("IX_FirstAndSecond", 2, IsUnique = true)]
public int SecondColumn { get; set; }
The second parameter in the attribute is where you can specify the order of the columns in the index.
More information: MSDN
I found three ways to solve the problem.
Unique indexes in EntityFramework Core:
First approach:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Entity>()
.HasIndex(p => new {p.FirstColumn , p.SecondColumn}).IsUnique();
}
The second approach to create Unique Constraints with EF Core by using Alternate Keys.
Examples
One column:
modelBuilder.Entity<Blog>().HasAlternateKey(c => c.SecondColumn).HasName("IX_SingeColumn");
Multiple columns:
modelBuilder.Entity<Entity>().HasAlternateKey(c => new [] {c.FirstColumn, c.SecondColumn}).HasName("IX_MultipleColumns");
EF 6 and below:
First approach:
dbContext.Database.ExecuteSqlCommand(string.Format(
#"CREATE UNIQUE INDEX LX_{0} ON {0} ({1})",
"Entitys", "FirstColumn, SecondColumn"));
This approach is very fast and useful but the main problem is that Entity Framework doesn't know anything about those changes!
Second approach:
I found it in this post but I did not tried by myself.
CreateIndex("Entitys", new string[2] { "FirstColumn", "SecondColumn" },
true, "IX_Entitys");
The problem of this approach is the following: It needs DbMigration so what do you do if you don't have it?
Third approach:
I think this is the best one but it requires some time to do it. I will just show you the idea behind it:
In this link http://code.msdn.microsoft.com/CSASPNETUniqueConstraintInE-d357224a
you can find the code for unique key data annotation:
[UniqueKey] // Unique Key
public int FirstColumn { get; set;}
[UniqueKey] // Unique Key
public int SecondColumn { get; set;}
// The problem hier
1, 1 = OK
1 ,2 = NO OK 1 IS UNIQUE
The problem for this approach; How can I combine them?
I have an idea to extend this Microsoft implementation for example:
[UniqueKey, 1] // Unique Key
public int FirstColumn { get; set;}
[UniqueKey ,1] // Unique Key
public int SecondColumn { get; set;}
Later in the IDatabaseInitializer as described in the Microsoft example you can combine the keys according to the given integer.
One thing has to be noted though: If the unique property is of type string then you have to set the MaxLength.
If you're using Code-First, you can implement a custom extension HasUniqueIndexAnnotation
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.Infrastructure.Annotations;
using System.Data.Entity.ModelConfiguration.Configuration;
internal static class TypeConfigurationExtensions
{
public static PrimitivePropertyConfiguration HasUniqueIndexAnnotation(
this PrimitivePropertyConfiguration property,
string indexName,
int columnOrder)
{
var indexAttribute = new IndexAttribute(indexName, columnOrder) { IsUnique = true };
var indexAnnotation = new IndexAnnotation(indexAttribute);
return property.HasColumnAnnotation(IndexAnnotation.AnnotationName, indexAnnotation);
}
}
Then use it like so:
this.Property(t => t.Email)
.HasColumnName("Email")
.HasMaxLength(250)
.IsRequired()
.HasUniqueIndexAnnotation("UQ_User_EmailPerApplication", 0);
this.Property(t => t.ApplicationId)
.HasColumnName("ApplicationId")
.HasUniqueIndexAnnotation("UQ_User_EmailPerApplication", 1);
Which will result in this migration:
public override void Up()
{
CreateIndex("dbo.User", new[] { "Email", "ApplicationId" }, unique: true, name: "UQ_User_EmailPerApplication");
}
public override void Down()
{
DropIndex("dbo.User", "UQ_User_EmailPerApplication");
}
And eventually end up in database as:
CREATE UNIQUE NONCLUSTERED INDEX [UQ_User_EmailPerApplication] ON [dbo].[User]
(
[Email] ASC,
[ApplicationId] ASC
)
The answer from niaher stating that to use the fluent API you need a custom extension may have been correct at the time of writing. You can now (EF core 2.1) use the fluent API as follows:
modelBuilder.Entity<ClassName>()
.HasIndex(a => new { a.Column1, a.Column2}).IsUnique();
You need to define a composite key.
With data annotations it looks like this:
public class Entity
{
public string EntityId { get; set;}
[Key]
[Column(Order=0)]
public int FirstColumn { get; set;}
[Key]
[Column(Order=1)]
public int SecondColumn { get; set;}
}
You can also do this with modelBuilder when overriding OnModelCreating by specifying:
modelBuilder.Entity<Entity>().HasKey(x => new { x.FirstColumn, x.SecondColumn });
For those finding this looking for a 2021 solution, the working version of the accepted answer should now look like this:
[Index(nameof(FirstColumn), nameof(SecondColumn), IsUnique = true)]
public class Entity
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public string EntityId { get; set;}
public int FirstColumn { get; set;}
public int SecondColumn { get; set;}
}
So that the annotation should live on the model and not the individual columns. Also note the nameof() syntax.
This answer was derived from the official documentation: https://learn.microsoft.com/en-us/ef/core/modeling/indexes?tabs=data-annotations
Completing #chuck answer for using composite indices with foreign keys.
You need to define a property that will hold the value of the foreign key. You can then use this property inside the index definition.
For example, we have company with employees and only we have a unique constraint on (name, company) for any employee:
class Company
{
public Guid Id { get; set; }
}
class Employee
{
public Guid Id { get; set; }
[Required]
public String Name { get; set; }
public Company Company { get; set; }
[Required]
public Guid CompanyId { get; set; }
}
Now the mapping of the Employee class:
class EmployeeMap : EntityTypeConfiguration<Employee>
{
public EmployeeMap ()
{
ToTable("Employee");
Property(p => p.Id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
Property(p => p.Name)
.HasUniqueIndexAnnotation("UK_Employee_Name_Company", 0);
Property(p => p.CompanyId )
.HasUniqueIndexAnnotation("UK_Employee_Name_Company", 1);
HasRequired(p => p.Company)
.WithMany()
.HasForeignKey(p => p.CompanyId)
.WillCascadeOnDelete(false);
}
}
Note that I also used #niaher extension for unique index annotation.
In the accepted answer by #chuck, there is a comment saying it will not work in the case of FK.
it worked for me, case of EF6 .Net4.7.2
public class OnCallDay
{
public int Id { get; set; }
//[Key]
[Index("IX_OnCallDateEmployee", 1, IsUnique = true)]
public DateTime Date { get; set; }
[ForeignKey("Employee")]
[Index("IX_OnCallDateEmployee", 2, IsUnique = true)]
public string EmployeeId { get; set; }
public virtual ApplicationUser Employee{ get; set; }
}
I assume you always want EntityId to be the primary key, so replacing it by a composite key is not an option (if only because composite keys are far more complicated to work with and because it is not very sensible to have primary keys that also have meaning in the business logic).
The least you should do is create a unique key on both fields in the database and specifically check for unique key violation exceptions when saving changes.
Additionally you could (should) check for unique values before saving changes. The best way to do that is by an Any() query, because it minimizes the amount of transferred data:
if (context.Entities.Any(e => e.FirstColumn == value1
&& e.SecondColumn == value2))
{
// deal with duplicate values here.
}
Beware that this check alone is never enough. There is always some latency between the check and the actual commit, so you'll always need the unique constraint + exception handling.
Recently added a composite key with the uniqueness of 2 columns using the approach that 'chuck' recommended, thank #chuck. Only this approached looked cleaner to me:
public int groupId {get; set;}
[Index("IX_ClientGrouping", 1, IsUnique = true)]
public int ClientId { get; set; }
[Index("IX_ClientGrouping", 2, IsUnique = true)]
public int GroupName { get; set; }
You should place Index attrib on top of the entity classs and define your multiple keys in string[]
[Index("FirstColumn", "SecondColumn", IsUnique = true, Name = "My_Unique_Index")]
public class Entity
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public string EntityId { get; set;}
public int FirstColumn { get; set;}
public int SecondColumn { get; set;}
}
I wanted to add my answer since the provided solutions did not help me. In my case one of the columns was a foreign key reference.
Old model:
public class Matrix
{
public int ID { get; set; }
public MachineData MachineData { get; set; }
public MachineVariant MachineVariant { get; set; }
}
Note that MachineVariant is an enum and MachineData is a reference.
Trying to use the provided solution by #Bassam Alugili:
modelBuilder.Entity<Matrix>()
.HasIndex(sm => new { sm.MachineData, sm.DoughVariant }).IsUnique(true);
Didn't work. So I added an ID column for the machineData foreign key like so:
public class Matrix
{
public int ID { get; set; }
public MachineData MachineData { get; set; }
[ForeignKey("MachineData")]
public int MachineDataID { get; set; }
public MachineVariant MachineVariant { get; set; }
}
And changed the modelbuilder code to this:
modelBuilder.Entity<Matrix>()
.HasIndex(sm => new { sm.MachineDataID, sm.DoughVariant }).IsUnique(true);
Which resulted in the desired solution
Related
Well, it is 1st time i am trying to create 1-1 relationship between two tables using code first. I took some help online and come across the following classes mapping.
Than I ran migration and found something wrong. E.g. The migration says that primary key for StudentDetails is Id from Student table whereas I am looking to have primary key StudentId. Also, the foreign key is being created in opposite way.
Please can someone highlight what is wrong here or is it me who perceived it wrong.
I need to use Id from student class as Foreign key in StudentDetails class.
public class Student
{
public bool isPass{get;set;}
public virtual StudentReport Report { get; set; }
}
public class StudentReport
{
[Key, ForeignKey("Student")]
public Guid Id { get; set; }
public Guid? StudentReportId { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public virtual Student Student { get; set; }
}
When i run my migration, i get the following outcome which looks not good.
public partial class StudentReport : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.StudentReport",
c => new
{
Id = c.Guid(nullable: false, identity: true),
StudentReportId = c.Guid(),
RollNumber = c.String(),
StudentType = c.String(),
})
.PrimaryKey(t => t.Id)
.ForeignKey("dbo.Student", t => t.Id)
.Index(t => t.Id);
}
In an one to one relationship one end must be the principal and the another one is the dependent. If you are going to declare a FK property in the dependent entity, EF requires that property should be PK too:
public class Principal
{
[Key]
public int Id{get;set;}
public virtual Dependent Dependent{get;set;}
}
public class Dependent
{
[Key, ForeignKey("Principal")]
public int PrincipalId{get;set;}
public virtual Principal Principal{get;set;}
}
If you want to have both entities with their own PKs, and also use Id from Student entity as FK in StudentReport class, then you can try with this model:
public class Student
{
[Key]
public Guid Id { get; set; }
public bool isPass{get;set;}
}
public class StudentReport
{
[Key]
public Guid StudentReportId{ get; set; }
[ForeignKey("Student")]
public Guid StudentId { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public virtual Student Student { get; set; }
}
I guess what you really need is an one to many relationship because an student could have 0 or many reports.
Check this link. It could help you understand better how to use the FK properties and the name conventions that have by default Code First.
Update 1
If you want to create an one to one relationship and both entities have their owns PKs, then you can't define a FK property in the dependent entity due to the restriction I explain at the begin of my answer. A solution for what you need could be using the Required attribute and deleting the FK property:
public class Student
{
[Key]
public Guid Id { get; set; }
public bool isPass{get;set;}
public virtual StudentReport StudentReport { get; set; }
}
public class StudentReport
{
[Key]
public Guid StudentReportId{ get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
[Required]
public virtual Student Student { get; set; }
}
Update 2
Are you sure? The migration code that I get is this:
AddForeignKey("dbo.StudentReports", "StudentReportId", "dbo.Students", "Id");
Which is not ok yet because Code First is still configuring by convention the PK of StudentReport as FK. To avoid that you can add this Fluent Api configuration to your context:
modelBuilder.Entity<StudentReport>()
.HasRequired(sr => sr.Student)
.WithOptional(s => s.StudentReport)
.Map(c=>c.MapKey("Student_Id"));
This way Code First will generate this migration code:
AddColumn("dbo.StudentReports", "Student_Id", c => c.Guid(nullable: false));
CreateIndex("dbo.StudentReports", "Student_Id");
AddForeignKey("dbo.StudentReports", "Student_Id", "dbo.Students", "Id");
I am trying to create one-to-many and reverse one-to-one relationship using code first. Here is what I ma trying to do
1) One-to-Many between two classes and it works as expected.
public class X
{
[Key]
public int XId { get; set; }
public ICollection<Y> Y { get; set; }
}
public class Y
{
[Key]
public int YId { get; set; }
public int XId { get; set; }
public X X { get; set; }
}
public class DataContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Y>()
.HasRequired(y => y.X)
.WithMany(x => x.Y)
.HasForeignKey(y => y.XId);
}
}
Now what I want to do is to create Reverse One-to-One optional relationship between Y and X, such that the X will contain a foreign key of Y...How is it possible? Here is what I am trying to do and it throws some Multiplicity Error
public class X
{
[Key]
public int XId { get; set; }
public ICollection<Y> Y { get; set; }
public int YId {get; set; }
[ForiegnKey("YId")]
public Y YOptional { get; set; }
}
public class Y
{
[Key]
public int YId { get; set; }
public int XId { get; set; }
public X X { get; set; }
public X XOptional {get; set; }
}
public class DataContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Y>()
.HasRequired(y => y.X)
.WithMany(x => x.Y)
.HasForeignKey(y => y.XId);
modelBuilder.Entity<X>()
.HasOptional(x => x.YOptional)
.WithOptionalDependent(y=> y.XOptional);
}
}
You can't have a relationship between two entities that is defined differently from either end. So you can't do 1:* from one direction and 1:1 from another.
Let me make a guess that you don't really want it to be 1:1 from the dependent end. From that end it will always only point to one thing.
In mappings, unlike in life, unless you have many to many, a child only has one parent.
You can, however, create a 0..1 : * relationaship (zero or one to many). Where the parent can have one or more children (e.g. "many") but the child can exist without a parent, but it can never have more than one parent (e.g. "zero or one").
Here is the simplest method of making your classes result in a [zero or one] to many relationship. Notice that I made the foreign key in the class Y a nullable int. WIth this setup, EF conventions will result in a mapping that lets a child exist without a parent.
public class X
{
[Key]
public int XId { get; set; }
public ICollection<Y> Y { get; set; }
}
public class Y
{
[Key]
public int YId { get; set; }
public int? XId { get; set; }
public X X { get; set; }
}
public class DataContext : DbContext
{
public DbSet<X> XSet { get; set; }
public DbSet<Y> YSet { get; set; }
}
Here is a screenshot of visual model derived from the above classes and context.
I think this achieves the behavior you are seeking if my guess that you may just be perceiving it differently is correct.
Using the actual class names you mentioned in the comments:
Mapping a User that can have many Singles is not a problem. However, when you want to map a 1:1 association between a User and a Single you have to choose which of the two is the "principle" entity. You can't have a foreign key column in both tables because one entity will always be inserted before the other one. The "dependent" entity is inserted next, and it refers to the principal's primary key value.
So if User is the principal entity, you could have a class model similar to this:
public class User
{
public User()
{
this.Singles = new HashSet<Single>();
}
public int UserId { get; set; }
public string Name { get; set; }
public Single Single { get; set; }
public virtual ICollection<Single> Singles { get; set; }
}
public class Single
{
public int SingleId { get; set; }
public string Name { get; set; }
public virtual User User { get; set; }
public int SuperUserId { get; set; }
public User SuperUser { get; set; }
}
And two options for mappings:
Option 1: User as principal
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<User>().HasMany(u => u.Singles)
.WithRequired(s => s.SuperUser).HasForeignKey(s => s.SuperUserId);
modelBuilder.Entity<User>().HasOptional(s => s.Single)
.WithOptionalPrincipal(s => s.User).Map(m => m.MapKey("UserId"));
}
In the data model, Single now has two foreign keys, UserId and SuperUserId. This is how to create a User and a Single in User.Single and User.Singles:
var superUser = new User { Name = "superUser1" };
var single = new Single { Name = "single" };
superUser.Singles.Add(single);
db.Users.Add(superUser);
superUser.Single = single;
db.SaveChanges();
And EF will first insert the User, then the Single having both foreign keys equal to the User's primary key.
Option 2: Single as principle
You can also make Single the principal entity in the 1:1 association:
modelBuilder.Entity<User>().HasOptional(s => s.Single)
.WithOptionalDependent(s => s.User).Map(m => m.MapKey("SingleId"));
Now there's only one foreign key in Single (SuperUserId) and a foreign key in User (SingleId). If you execute the same code, now EF will throw
Unable to determine a valid ordering for dependent operations.
This is because there is a chicken-and-egg problem: the Single must be created before the dependent User can be created, but the User must be created before the Single can be added to its Singles collection. This could be solved by assigning the Single later:
var superUser = new User { Name = "superUser1" };
var single = new Single { Name = "single" };
superUser.Singles.Add(single);
db.Users.Add(superUser);
db.SaveChanges();
superUser.Single = single;
db.SaveChanges();
You'd want to wrap this in a TransactionScope, so I think this option is less viable.
Note
As you see, in a 1:1 mapping the foreign key can't be mapped to a property in the class model. There is no HasForeignKey in the fluent API after WithOptionalDependent or WithOptionalPrincipal. Also, this association can only be mapped by the fluent API. In data annotations there is not attribute to indicate the principal end of an association.
This may be a duplicate qn, but i couldnt get a proper answer to this scenario. I have the following table structure:
public class File
{
public int FileId { get; set; } //PK
public int VersionID { get; set; }
public virtual ICollection<FileLocal> FileLLocalCollection { get; set; }
}
public class FileLocal
{
public int FileId { get; set; } //PK, FK
public int LangID { get; set; } //PK,FK
public string FileName { get; set; }
}
I have not included the third table here(Its basically LangID (PK) & LangCode )
How do i specify this mapping in fluent Api so that i can load "FileLLocalCollection" with every File objects?
The first part of your mapping can be done this way:
modelBuilder.Entity<File>()
.HasMany(f => f.FileLocalCollection)
.WithRequired()
.HasForeignKey(fl => fl.FileId);
modelBuilder.Entity<FileLocal>()
.HasKey(fl => new {fl.FileId, fl.LangId});
And the second part depends on the way how your Lang is defined. For example if you add navigation property from FileLocal to Lang you can map it this way:
modelBuilder.Entity<FileLocal>()
.HasRequired(fl => fl.Lang)
.WithMany()
.HasForeignKey(fl => fl.LangId);
I am using EF 4.1 code first and I am struggling with the association entity and getting the value that was set in the association table. I tried to follow the post on: Create code first, many to many, with additional fields in association table.
My tables are as follows (all are in plural form):
Table: Products
Id int
Name varchar(50)
Table: Specifications
Id int
Name varchar(50)
Table: ProductSpecifications
ProductId int
SpecificationId int
SpecificationValue varchar(50)
My related classes:
public class Product : IEntity
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<ProductSpecification> ProductSpecifications { get; set; }
}
public class Specification : IEntity
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<ProductSpecification> ProductSpecifications { get; set; }
}
public class ProductSpecification
{
public int ProductId { get; set; }
public virtual Product Product { get; set; }
public int SpecificationId { get; set; }
public virtual Specification Specification { get; set; }
public string SpecificationValue { get; set; }
}
My context class:
public class MyContext : DbContext
{
public DbSet<Product> Products { get; set; }
public DbSet<Specification> Specifications { get; set; }
public DbSet<ProductSpecification> ProductSpecifications { get; set; }
protected override void OnModelCreating(DbModelBuilder dbModelBuilder)
{
}
}
My repository method where I do my call (not sure if it is correct):
public class ProductRepository : IProductRepository
{
MyContext db = new MyContext();
public Product GetById(int id)
{
var product = db.Products
.Where(x => x.Id == id)
.Select(p => new
{
Product = p,
Specifications = p.ProductSpecifications.Select(s => s.Specification)
})
.SingleOrDefault();
return null; // It returns null because I don't know how to return a Product object?
}
}
Here is the error that I am getting back:
One or more validation errors were detected during model generation:
System.Data.Edm.EdmEntityType: : EntityType 'ProductSpecification' has no key defined. Define the key for this EntityType.
System.Data.Edm.EdmEntitySet: EntityType: EntitySet �ProductSpecifications� is based on type �ProductSpecification� that has no keys defined.
What does it mean that no keys are defined? Won't the ProductId and SpecificationId map to Id of Product and Id of Specification respectively?
How would I return a single product with the all the specifications for it?
Entity Framework will recognize that ProductId is a foreign key property for the Product navigation property and SpecificationId is a foreign key property for the Specification navigation property. But the exception complains about a missing primary key ("Key" = "Primary Key") on your ProductSpecification entity. Every entity needs a key property defined. This can happen either by conventions - by a specific naming of the key property - or explicity with data annotations or Fluent API.
Your ProductSpecification class doesn't have a property which EF would recognize as a key by convention: No Id property and no ProductSpecificationId (class name + "Id").
So you must define it explicitely. Defining it with data annotations is shown in the post you linked:
public class ProductSpecification
{
[Key, Column(Order = 0)]
public int ProductId { get; set; }
public virtual Product Product { get; set; }
[Key, Column(Order = 1)]
public int SpecificationId { get; set; }
public virtual Specification Specification { get; set; }
public string SpecificationValue { get; set; }
}
And in Fluent API it would be:
modelBuilder.Entity<ProductSpecification>()
.HasKey(ps => new { ps.ProductId, ps.SpecificationId });
Both ways define a composite key and each of the parts is a foreign key to the Product or Specification table at the same time. (You don't need to define the FK properties explicitely because EF recognizes it due to their convention-friendly names.)
You can return a product including all specifications with eager loading for example:
var product = db.Products
.Include(p => p.ProductSpecifications.Select(ps => ps.Specification))
.SingleOrDefault(x => x.Id == id);
I have a User < Country model. A user belongs to a country, but may not belong to any (null foreign key).
How do I set this up? When I try to insert a user with a null country, it tells me that it cannot be null.
The model is as follows:
public class User{
public int CountryId { get; set; }
public Country Country { get; set; }
}
public class Country{
public List<User> Users {get; set;}
public int CountryId {get; set;}
}
Error: A foreign key value cannot be inserted because a corresponding primary key value does not exist. [ Foreign key constraint name = Country_Users ]"}
You must make your foreign key nullable:
public class User
{
public int Id { get; set; }
public int? CountryId { get; set; }
public virtual Country Country { get; set; }
}
I prefer this (below):
public class User
{
public int Id { get; set; }
public int? CountryId { get; set; }
[ForeignKey("CountryId")]
public virtual Country Country { get; set; }
}
Because EF was creating 2 foreign keys in the database table: CountryId, and CountryId1, but the code above fixed that.
I have the same problem now ,
I have foreign key and i need put it as nullable,
to solve this problem you should put
modelBuilder.Entity<Country>()
.HasMany(c => c.Users)
.WithOptional(c => c.Country)
.HasForeignKey(c => c.CountryId)
.WillCascadeOnDelete(false);
in DBContext class
I am sorry for answer you very late :)
I recommend to read Microsoft guide for use Relationships, Navigation Properties and Foreign Keys in EF Code First, like this picture.
Guide link below:
https://learn.microsoft.com/en-gb/ef/ef6/fundamentals/relationships?redirectedfrom=MSDN