EF Fluent API + two column composite uniqueness + autoincrement primary key

Question

1. I use Fluent API. I don't like annotations.

2. I like to always use an autoincrement as my primary key, in all of my tables.

3. Some of my tables require that two columns, X and Y (where X is not the autoincrement key and Y is not the autoincrement key) have to be unique, ie: there can't be another row such that it has X1=X2 and Y1=Y2. If I wasn't using an autoincrement key, I would simply make these two the key, like this:

       modelBuilder.Entity<Foo>()
           .HasKey(t => new { t.X, t.Y })
           .ToTable("Foos");
   

   But, as I said in (2), I'm using autoincrement primary keys

       modelBuilder.Entity<Foo>()
           .HasKey(t => t.someLongId)
           .ToTable("Foos");
   

How can I achieve this composite uniqueness in Fluent API?

This is what I want to achieve, written in SQL:

CREATE  TABLE `Foos` (
  `ID` BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT ,
  ...
  PRIMARY KEY (`ID`),
  UNIQUE KEY (`X`, `Y`) 
);

Answer 1

You can achieve this using the 'HasColumnAnnotation(...)' method and applying an IndexAnnotation > IndexAttribute.

modelBuilder.Entity<Foo>() 
            .Property(t => t.X) 
            .HasColumnAnnotation("X", new IndexAnnotation(new IndexAttribute("X") { IsUnique = true }));

You can find further information here (MSDN)

Answer 2

Aydin's answer had the concept (IndexAnnotation and HasColumnAnnotation) but it wasn't involving the other columns. Here is a complete answer that worked for me:

modelBuilder
    .Entity<Foo>()
    .Property(t => t.X)
    .IsRequired()
    .HasMaxLength(60)
    .HasColumnAnnotation(IndexAnnotation.AnnotationName, new IndexAnnotation(new IndexAttribute("IX_X_Y", 1) { IsUnique = true }));

modelBuilder
    .Entity<Foo>()
    .Property(t => t.Y)
    .IsRequired()
    .HasColumnAnnotation(IndexAnnotation.AnnotationName, new IndexAnnotation(new IndexAttribute("IX_X_Y", 2) { IsUnique = true }));

That, supposing that X is string column and Y is not (just to show how .HasMaxLength(60) can be used in the string column)

I will accept Aydin's answer though.