The `[IndexColumn]` attribute that is the revival of `[Index]` attribute for EF Core. (with extension for model building.)
This package also provides [PrimaryKey] attribute.
Annotate your model with [IndexColumn] attribute that lives in Toolbelt.ComponentModel.DataAnnotations.Schema.V5 namespace.
Notice - The attribute name is [IndexColumn], is not [Index] (the attribute name [Index] is used by EFocre v.5.0).
using Toolbelt.ComponentModel.DataAnnotations.Schema.V5;
public class Person
{
public int Id { get; set; }
[IndexColumn] // <- Here!
public string Name { get; set; }
}
[Important] Override OnModelCreating() method of your DbContext class, and call BuildIndexesFromAnnotations() extension method which lives in Toolbelt.ComponentModel.DataAnnotations namespace.
using Microsoft.EntityFrameworkCore;
using Toolbelt.ComponentModel.DataAnnotations;
public class MyDbContext : DbContext
{
...
// Override "OnModelCreating", ...
protected override void OnModelCreatin(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
// .. and invoke"BuildIndexesFromAnnotations"!
modelBuilder.BuildIndexesFromAnnotations();
}
}
If you use SQL Server and IsClustered=true and/or Includes = new[]{"Foo", "Bar"} features, you need to call BuildIndexesFromAnnotationsForSqlServer() extension method instead of BuildIndexesFromAnnotations() extension method.
BuildIndexesFromAnnotations() (or, BuildIndexesFromAnnotationsForSqlServer()) extension method scans the DbContext with .NET Reflection technology, and detects [IndexColumn] attributes, then build models related to indexing.
After doing that, the database which created by EF Core, contains indexes that are specified by [IndexColumn] attributes.
Appendix A - Suppress "NotSupportedException"
You will run into "NotSupportedException" when you call BuildIndexesFromAnnotations() with the model which is annotated with the [IndexColumn] attribute that's "IsClustered" property is true, or "Includes" property is not empty.
If you have to call BuildIndexesFromAnnotations() in this case (for example, share the model for different Database products), you can suppress this behavior with configuration, like this.
If you annotate the model with "IsClustered=true" index simply like this,
public class Employee {
public int Id { get; set; }
[IndexColumn(IsClustered = true)]
public string EmployeeCode { get; set; }
}
You will run into 'System.Data.SqlClient.SqlException' like this.
System.Data.SqlClient.SqlException :
Cannot create more than one clustered index on table '(table name)'.
Drop the existing clustered index '(index name)' before creating another.
In this case, you need to annotate a primary key property with [PrimaryKey(IsClustered = false)] attribute explicitly for suppress auto generated primary key to be clustered index.
public class Employee {
[PrimaryKey(IsClustered = false)] // <- Add this line!
public int Id { get; set; }
[IndexColumn(IsClustered = true)]
public string EmployeeCode { get; set; }
}
Appendix C - If you want to use only "IndexAttribute" without any dependencies...
