Welcome to the first in a series of blog posts on my proposed migrations framework for NHibernate.  This series will be updated once the feature is finalized.

The fork of NHibernate is in my github repo along with a demo of how to use the migrations. 

The Short Version

Implement migrations by inheriting from FluentMigration as such

	public class InitialMigration : FluentMigration
	{
		public InitialMigration() 
			: base("2014-09-23_152150_InitialMigration", "NHMigrationExample"){}

		protected override void BuildOperations(IDdlOperationBuilderSurface builder)
		{
			builder.Create.Table("`NHibernateMigrationHistory`", c => new
			{
				Context = c.String(255, nullable:false),
				Version = c.String(255, nullable: false),
				Configuration = c.BinaryBlob(2147483647)
			}).PrimaryKey(c => new{ c.Context, c.Version});

			builder.Create.Table("`Cat`", c => new
			{
				Id = c.Int32(nullable: false),
				Name = c.String(255)
			}).PrimaryKey(x => x.Id, isIdentity: true);
		}

		protected override Configuration GetConfiguration()
		{
			return new Configuration();
		}
	}

	public class AddedDog : FluentMigration
	{
		public AddedDog()
			: base("2014-09-23_154250_AddedDog", "NHMigrationExample"){}

		protected override void BuildOperations(IDdlOperationBuilderSurface builder)
		{

			builder.Alter.Table("`Cat`").AddColumn("Color", c => c.String(255));

			builder.Create.Table("`Dog`", c => new
			{
				Id = c.Int32(nullable: false),
				Name = c.String(255)
			}).PrimaryKey(x => x.Id, isIdentity: true);

		}

		protected override Configuration GetConfiguration()
		{
			return new Configuration();
		}
	}

When you set up your configuration call:

    cfg.UseTableBasedMigrations(Context: "NHMigrationExample");
    cfg.RegisterAllMigrationsFrom(Assembly: typeof(MyAppConfiguration).Assembly);

then during application start-up call ISessionFactory.MigrateToLatestVersion()

    var sessionFactory = cfg.BuildSessionFactory();
    sessionFactory.MigrateToLatestVersion();