Why Migrations are not using EntityTypeConfiguration?

I have a project in Asp.Net MVC using Migrations.

The problem is that when I run the migration it creates additional properties which I didnt declared in my models.

Example for 'User' model:

public int Id { get; set; }

public string Nome { get; set; }

public int IdPosition { get; set; }

[Required]

public string Username { get; set; }

[Required]

[DataType(DataType.Password)]

public string Password { get; set; }

public virtual Position position { get; set; }

When I run the migration it creates an additional property called position_Id and maps it as the foreign key. Like Below:

CreateTable(

"dbo.User",

c => new

{

Id = c.Int(nullable: false, identity: true),

Name = c.String(nullable: false, maxLength: 100, unicode: false),

IdPosition = c.Int(nullable: false),

Username = c.String(nullable: false, maxLength: 100, unicode: false),

Password = c.String(nullable: false, maxLength: 100, unicode: false),

position_Id = c.Int(), //Does not exist on model neither on EntityTypeConfig file

})

.PrimaryKey(t => t.Id)

.ForeignKey("dbo.Position", t => t.position_Id)

.Index(t => t.position_Id); //does not exist on model neither on EntityTypeConfig file.

But I have already declared IdPosition as the Foreign Key on EntityTypeConfiguration file.cs, Like this:

protected override void ConfigForeignKey()

{

HasRequired(k => k.position)

.WithMany()

.HasForeignKey(fk => fk.IdPosition)

.WillCascadeOnDelete(false);

}

I Really need to know what I'm doing wrong. Thanks on advance