How to create index in Entity Framework 6.2 with code first

Is there a way to create an index on a property/column using code-first, instead of using the new IndexAttribute ?

Well 26.10.2017 Entity Framework 6.2 was officially released. It includes a possibility to define indexes with ease via Fluent API. Ho it is to use was already announced in the beta of 6.2.

Now you can use the HasIndex() method, followed by IsUnique() if it should be an unique index.

Just a small comparison (before/after) example:

// before 
modelBuilder.Entity<Person>()
        .Property(e => e.Name)
        .HasColumnAnnotation(
            IndexAnnotation.AnnotationName, 
            new IndexAnnotation(new IndexAttribute { IsUnique = true }));

// after
modelBuilder.Entity<Person>()
    .HasIndex(p => p.Name)
    .IsUnique();

// multi column index
modelBuilder.Entity<Person>()
    .HasIndex(p => new { p.Name, p.Firstname })
    .IsUnique();

It is also possible to mark the index as clustered with .IsClustered().

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EDIT #1

Added an example for multi column index and additional information how to mark an index as clustered.

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EDIT #2

As additional information, in EF Core 2.1 it is exactly the same like in EF 6.2 now.
Here is the MS Doc artcile as reference.

Currently there is no "first class support" for creating a index via the fluent API, but what you can do is via the fluent API you can mark properties as having attributes from the Annotation API. This will allow you to add the Index attribute via a fluent interface.

Here are some examples from the work item from Issues site for EF.

Create a index on a single column:

modelBuilder.Entity<MyEntity>()
    .Property(e => e.MyProperty)
    .HasColumnAnnotation(
        IndexAnnotation.AnnotationName, 
        new IndexAnnotation(new IndexAttribute()));

Multiple indexes on a single column:

modelBuilder.Entity<MyEntity>()
    .Property(e => e.MyProperty)
    .HasColumnAnnotation(
        IndexAnnotation.AnnotationName, 
        new IndexAnnotation(new[]
            {
                new IndexAttribute("Index1"),
                new IndexAttribute("Index2") { IsUnique = true }
            }));

Multi-Column indexes:

modelBuilder.Entity<MyEntity>()
    .Property(e => e.MyProperty1)
    .HasColumnAnnotation(
        IndexAnnotation.AnnotationName,
        new IndexAnnotation(new IndexAttribute("MyIndex", 1)));

modelBuilder.Entity<MyEntity>()
    .Property(e => e.MyProperty2)
    .HasColumnAnnotation(
        IndexAnnotation.AnnotationName, 
        new IndexAnnotation(new IndexAttribute("MyIndex", 2)));

Using the above techniques will cause .CreateIndex() calls to be automatically created for you in your Up() function when you scaffold your next migration (or be automatically created in the database if you are not using migrations).

I've created a some extension methods and wrapped them in a nuget package to make this much easier.

Install the EntityFramework.IndexingExtensions nuget package.

Then you can do the following:

public class MyDataContext : DbContext
{
  protected override void OnModelCreating(DbModelBuilder modelBuilder)
  {
    modelBuilder.Entity<Customer>()
        .HasIndex("IX_Customers_Name",          // Provide the index name.
            e => e.Property(x => x.LastName),   // Specify at least one column.
            e => e.Property(x => x.FirstName))  // Multiple columns as desired.

        .HasIndex("IX_Customers_EmailAddress",  // Supports fluent chaining for more indexes.
            IndexOptions.Unique,                // Supports flags for unique and clustered.
            e => e.Property(x => x.EmailAddress)); 
  }
}

The project and source code are here. Enjoy!

Without an explicit name:

[Index]
public int Rating { get; set; } 

With a specific name:

[Index("PostRatingIndex")] 
public int Rating { get; set; }

From EF 6.1 onward the attribute [Index] is supported.
Use [Index(IsUnique = true)] for unique index.
Here is the link from Microsoft

public class User 
{ 
    public int UserId { get; set; } 
 
    [Index(IsUnique = true)] 
    [StringLength(200)] 
    public string Username { get; set; } 
 
    public string DisplayName { get; set; } 
}

Entity Framework 6

Property(c => c.MyColumn)
        .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("IX_MyIndex")));

And add using:

using System.Data.Entity.Infrastructure.Annotations;
using System.ComponentModel.DataAnnotations.Schema;

You can use the INDEX data annotaion Code First Data Annotations

If you don't want to use attributes on your POCO's, then you can always do it like the following:

context.Database.ExecuteSqlCommand("CREATE INDEX IX_NAME ON ..."); 

You can execute this statement in your custom DbInitializer derived class. I don't know any Fluent API way of doing this though.

You can use one of this

// Indexes

 this.HasIndex(e => e.IsActive)
            .HasName("IX_IsActive");

or

  this.Property(e => e.IsActive).HasColumnAnnotation(
            "Index",
            new IndexAnnotation(new IndexAttribute("IX_IsActive")));

I write an extension method for use in fluent EF to avoid extra code:

public static PrimitivePropertyConfiguration HasIndexAnnotation(
    this PrimitivePropertyConfiguration primitivePropertyConfiguration, 
    IndexAttribute indexAttribute = null
    )
{
    indexAttribute = indexAttribute ?? new IndexAttribute();

    return primitivePropertyConfiguration
        .HasColumnAnnotation(
            IndexAnnotation.AnnotationName, 
            new IndexAnnotation(indexAttribute)
        );
}

then use it like this:

Property(t => t.CardNo)
    .HasIndexAnnotation();

or like this if index needs some configs:

Property(t => t.CardNo)
    .HasIndexAnnotation(new IndexAttribute("IX_Account") { IsUnique = true });