CODEWITHSUNDEEP
entity-frameworkentity-framework-coreentity-framework-4.1code-first
GilShalit
GilShalit

Reputation: 6463

in entity framework code first, how to use KeyAttribute on multiple columns

I'm creating a POCO model to use with entity framework code first CTP5. I'm using the <key()> decoration to make a property map to a PK column. But how can I define a PK on more then one column, and specifically, how can I control order of the columns in the index? Is it a result of the order of properties in the class?

Edit: look at @kara's answer for an updated solution.

Thanks!

Upvotes: 116

Views: 90581

Answers (6)

ساناز جواهری
ساناز جواهری

Reputation: 21

In EF or EF Core, the Column Order attribute is not supported for specifying key order, so the best practice is to configure composite keys in the OnModelCreating method of your DbContext.

public class MyEntity
{
    public int MyFirstKeyProperty { get; set; }

    public int MySecondKeyProperty { get; set; }

    public string MyThirdKeyProperty { get; set; }

    // Other properties
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<MyEntity>()
        .HasKey(e => new { e.MyFirstKeyProperty, e.MySecondKeyProperty, e.MyThirdKeyProperty });

    base.OnModelCreating(modelBuilder);
}

Upvotes: 1

kara
kara

Reputation: 3455

In EF Core 7.0 a new attribute for classes [PrimaryKey] was introduced.

Example:

[PrimaryKey(nameof(FirstName),nameof(LastName))]
public class Person
{
    public string FirstName { get; set; }

    public string LastName { get; set; }

    public string SomeProperty { get; set; }
}

This way, you don't have to use the fluent-api again.

Upvotes: 15

Slauma
Slauma

Reputation: 177133

NOTE: As of 2019 this answer became non-valid for later EntityFramework versions.

You can specify the column order in the attributes, for instance:

public class MyEntity
{
    [Key, Column(Order=0)]
    public int MyFirstKeyProperty { get; set; }

    [Key, Column(Order=1)]
    public int MySecondKeyProperty { get; set; }

    [Key, Column(Order=2)]
    public string MyThirdKeyProperty { get; set; }

    // other properties
}

If you are using the Find method of a DbSet you must take this order for the key parameters into account.

Upvotes: 172

WACS kumara
WACS kumara

Reputation: 11

Use as a anonymous object:

modelBuilder.Entity<UserExamAttemptQuestion>().ToTable("Users").HasKey(o => new { o.UserId, o.Username });

Upvotes: 1

Daniele Armanasco
Daniele Armanasco

Reputation: 7451

If, like me, you prefer to use a configuration file you can do that in this way (based on Manavi's example):

public class User
{
    public int UserId { get; set; }
    public string Username { get; set; }
}  

public class UserConfiguration : EntityTypeConfiguration<User>
{
    public UserConfiguration()
    {
        ToTable("Users");
        HasKey(x => new {x.UserId, x.Username});
    }
}

Obviously you have to add the configuration file to your context:

public class Ctp5Context : DbContext
{
    public DbSet<User> Users { get; set; }        

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
         modelBuilder.Configurations.Add(new UserConfiguration());
    }
}

Upvotes: 13

Morteza Manavi
Morteza Manavi

Reputation: 33206

To complete the correct answer submitted by Slauma, you can use the HasKey method to specify an order for composite primary keys as well:

public class User
{        
    public int UserId { get; set; }       
    public string Username { get; set; }        
}        

public class Ctp5Context : DbContext
{
    public DbSet<User> Users { get; set; }        

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>().HasKey(u => new 
        { 
            u.UserId, 
            u.Username 
        });
    }
}

Upvotes: 75

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