EF Foreign Key using Fluent API

c# entity-framework

Question

Here are my models. I have one to one mapping for Vehicle and Driver. I will have the vehicle created first and then map the driver to the vehicle.

public class Driver
{
    public int Id { get; set; }
    public String Name { get; set; }
    public int VehicleId { get; set; }
    public virtual Vehicle Vehicle  { get; set; }
}

public class Vehicle
{  
    public int Id { get; set; }
    public String Name { get; set; }

    public virtual Driver Driver { get; set; }

    public int VehicleGroupId { get; set; }
    public virtual VehicleGroup Vehicles { get; set; }
}

I want to use VehicleId property in Driver class to keep id of vehicle the driver is driving.

I've written the following Fluent API code:

modelBuilder.Entity<Vehicle>()
            .HasRequired(d => d.Driver)
            .WithRequiredPrincipal();

But it creates a new column in Drivers table - Vehicle_VehicleId and maps it to the VehicleId on Vehicle table. I want the VehicleId of Driver table to map.

Also, i'm brand new to EF and Fluent API. I find it extremely confusing choosing between WithRequiredDependent and WithRequiredPrincipal. Would be glad if you can describe it in simple words. Thanks.

1
14
1/20/2014 8:36:57 AM

Fastest Entity Framework Extensions

Bulk Insert
Bulk Delete
Bulk Update
Bulk Merge

Accepted Answer

This line:

public int VehicleId { get; set; }

is telling EF, through code-conventions, that you want a foreign key in Driver pointing to Vehicle.

The following is telling EF that you want a 1:1 relationship from Driver to Vehicle:

public virtual Vehicle Vehicle { get; set; }

You should remove both and stick with your Fluent API configuration.

Regarding WithRequiredPrincipal vs. WithRequiredDependent:

You are specifying a compulsory relationship between Vehicle and Driver, with navigation from Vehicleto Driver, thus: Vehicle 1 --> 1 Driver

(Vehicle is the principal and Driver the dependent, since the navigation property is located in Vehicleand pointing to Driver .)

modelBuilder.Entity<Vehicle>()
            .HasRequired(d => d.Driver)
            .WithRequiredDependent();

You are specifying a compulsory relationship between Vehicle and Driver, with navigation from Driver to Vehicle, thus: Vehicle 1 <-- 1 Driver

(Vehicle is the dependent and Driver the principal, since the navigation property is located in Driver pointing to Vehicle.)

These two are analogous:

modelBuilder.Entity<Vehicle>()
            .HasRequired(v => v.Driver)
            .WithRequiredPrincipal();

modelBuilder.Entity<Driver>()
            .HasRequired(d => d.Vehicle)
            .WithRequiredDependent();
24
12/20/2018 8:05:38 AM

Popular Answer

EF creates the Vehicle_VehicleId column because you have VehicleId and Vehicle on your Driver Entity.

Remove VehicleId and Vehicle from your Driver Entity:

public class Driver
{
    public int Id { get; set; }
    public String Name { get; set; }
}

public class Vehicle
{  
    public int Id { get; set; }
    public String Name { get; set; }
}

Using:

modelBuilder.Entity<Vehicle>()
        .HasRequired(d => d.Driver)
        .WithRequiredPrincipal();

you are setting the relationship so no need to include manual properties in your entity classes.

You get the VehicleId from the navigation property Vehicle:

IQueryable<int> vehicleIds = context.Drivers.Select(x => x.Id == 123).Vehicles.Id;
Sam Leach

Related Questions

From a foreign key in a table, EF does not construct a foreign key association.

I found the solution here:...Why doesn't EF 4 generate association for FK relation to column with unique index?...The reason it was not recognizing it is was because the table had a unique non-clustered index on the foreign key field....Apparently, a unique, non-clustered index allows for a null value which can't be mapped.
entity-framework
asked by rsteckly

First, define the Foreign Key Entity Framework Code, then use Fluent Api.

I do not see a problem with the use of fluent API here. If you do not want the collection navigational property(ie: ...Cars...) on the ...Person... class you can use the argument less ...WithMany... method.
ef-code-first entity-framework fluent-interface foreign-keys
asked by Eranga

EF Code First Fluent API specifying the Foreign Key property

I prefer to use Data Annotations for these tasks, not Fluent API. It is much shorter end easy to understand. EF must detect properties ended with "Id" automatically, but to be on a safe side you can specify them explicitly:...using System.ComponentModel.DataAnnotations.Schema; ... public int AgentId { get; set; } [ForeignKey("AgentId")] public vir...
ef-code-first entity-framework
asked by fifonik

EF Composite key fluent API

As it turned out, I simply forgot putting the map on the DbContext:...modelBuilder.Configurations.Add(new CustomerImageMap()); ...That said, the composite Id still not being populated on the $metadata this way. And so using data annotaion this is the metadata that is generated:...<EntityType Name="CustomerImage"> <Key> <PropertyRef Name...
c# composite-key composite-primary-key entity-framework fluent
asked by Tomer

EF6 Code First: Using Fluent API to declare a Foreign Key

My problem was conceptual. While typically an Identity would only apply to one Account (leading me to visualize it as a 1:1), theoretically the Identity could be used more then once and therefore on more then one Account. If I use the following configuration, I get what I was looking for. Its then up to me to enforce any rules such as an Identity c...
c# ef-code-first entity-framework
asked by Steve Wash

How to add a composite unique key using EF 6 Fluent Api?

Here is an example showing how to create a composite unique key via fluent API. The composite key consists of ProjectId and SectionOdKey....public class Table { int Id{set;get;} int ProjectId {set;get;} string SectionOdKey{set;get;} } public class TableMap : EntityTypeConfiguration<Table> { this.Property(t => t.ProjectId).HasCol...
c# entity-framework
asked by Bargitta

EF 6 Codefirst -Setting default value for a property defined in base class using fluent API

There is no way to do this. It can't set default values with Entity Framework. Instead you can use the constructor...public abstract class BaseModel { protected BaseModel() { IsActive = true; } }
ef-fluent-api entity-framework entity-framework-6
asked by Marc Cals

Navigation property without foreign key, or fluent api version?

I tried the other way, created one such ...Employee... table and added as a model, it got me this:...public partial class Employee { public Employee() { Subordinates = new HashSet<Employee>(); } public int Id { get; set; } public string Name { get; set; } public int? ManagerId { get; set; } public virtual Employe...
c# ef-code-first ef-migrations entity-framework entity-framework-6
asked by singsuyash

How to use the fluent api to set a foreign key in EF 6

Maped to the navigation property, you should add virtual property of type User than map to:...public class User { [Key] public int id { get; set; } public int UserId { get; set; } public virtual User User{get;set;} } // ... modelBuilder.Entity<User>().HasOptional<User>(x=> x.User); ...Read more about relation-ships ...here
c# entity-framework-6 foreign-keys
asked by Henka Programmer

How can I set the foreign key name using the Fluent API with Code First Migrations?

Unfortunately, in EF6 there is no built-in way to do this. To clarify your question a little, What you are asking is how to specify the name of the underlying database constraint that is created based on the foreign key specified in your model. This would be a job for the migration generator. Though the functionality is there in EF6 migrations t...
c# ef-migrations entity-framework-6 fluent vb.net
asked by Dimitri

Fastest Entity Framework Extensions

Bulk Insert
Bulk Delete
Bulk Update
Bulk Merge
View more on Stack Overflow

Prime Library

Performance

Expression Evaluator

More Projects...

Related

Licensed under: CC-BY-SA with attribution
Not affiliated with Stack Overflow
Licensed under: CC-BY-SA with attribution
Not affiliated with Stack Overflow