Creating Unique Index with Entity Framework 6.1 fluent API

.net c# entity-framework entity-framework-6 fluent-interface

Question

I have a column "Name" that must be unqiue. No foreign key or anything like that.

EF 6.1 finally supports creating such indexes via Annotations. That has been discussed already on SO. But it seems it can only be done via annotations in the classes. How do I do that using only the Fluent API?

Something like this:

public class PersonConfiguration : EntityTypeConfiguration<Person>
{
    public PersonConfiguration()
    {
        HasKey(p => p.Id);
        Property(p => p.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

        //not possible?
        Index(p => p.Name).IsUnique();  //???
    }
}
1
38
2/27/2017 8:03:14 AM

Accepted Answer

NOTE: Relevant to EF 6

You can use IndexAttribute as mentioned but with Fluent API instead of DataAnnotations which will do the trick:

modelBuilder 
    .Entity<Person>() 
    .Property(t => t.Name) 
    .HasColumnAnnotation( 
        "Index",  
        new IndexAnnotation(new IndexAttribute("IX_Name") { IsUnique = true }));

Unfortunately there is no other way to create unique indexes using Fluent API. There is an open issue regarding this feature: Unique Constraints (Unique Indexes)


UPDATE: Entity Framework Core

In the latest EF Core release you can rely on Fluent API to specify indexes without additional tricks.
HasIndex allows to define it:

modelBuilder 
    .Entity<Person>()
    .HasIndex(x => x.Name);

Hence it returs IndexBuilder object you can use it for further index configurations (i.e uniqueness):

modelBuilder 
    .Entity<Person>()
    .HasIndex(x => x.Name)
    .IsUnique();
58
5/16/2018 11:47:07 AM

Popular Answer

Based on Anatolii's answer, here is an extension method for setting unique indexes more fluently:

public static class MappingExtensions
{
    public static PrimitivePropertyConfiguration IsUnique(this PrimitivePropertyConfiguration configuration)
    {
        return configuration.HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute { IsUnique = true }));
    }
}

Usage:

modelBuilder 
    .Entity<Person>() 
    .Property(t => t.Name)
    .IsUnique();

Will generate migration such as:

public partial class Add_unique_index : DbMigration
{
    public override void Up()
    {
        CreateIndex("dbo.Person", "Name", unique: true);
    }

    public override void Down()
    {
        DropIndex("dbo.Person", new[] { "Name" });
    }
}


Related Questions





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