Fluent NHibernate - always drop table - sql-server-2008

Question

Hi I start learn Fluent NHibernate. I am using this tutorial http://www.d80.co.uk/post/2011/02/20/Linq-to-NHibernate-Tutorial.aspx.
Here is my sample code:
public class Account
{
public virtual int Id { get; set; }
public virtual string Nick { get; set; }
public virtual string Password { get; set; }
}
public class AccountMap:ClassMap<Account>
{
public AccountMap()
{
Id(x => x.Id);
Map(x => x.Nick);
Map(x => x.Password);
}
}
public class NHiberanteHelper
{
private static ISessionFactory _sessionFactory;
private static ISessionFactory SessionFactory
{
get
{
if (_sessionFactory == null)
InitializeSessionFactory();
return _sessionFactory;
}
}
private static void InitializeSessionFactory()
{
_sessionFactory = Fluently.Configure()
//NHibernate bude pouzivat ovladace pre MS SQL 2008
.Database(MsSqlConfiguration.MsSql2008
.ConnectionString(
#"Server=JAN-MSI\SQLEXPRESS;Database=SimpleNHibernate;Trusted_Connection=True;").ShowSql()
)
//urci NHibernatu kde ma hladat mapovacie subory
.Mappings(m=>m.FluentMappings.AddFromAssemblyOf<Account>())
//ak tabs nie su v DB vytvori
.ExposeConfiguration(cfg => new SchemaExport(cfg).Create(true, true))
//vytvori jeden session pre cely life-time apps
.BuildSessionFactory();
}
public static ISession OpenSession()
{
return SessionFactory.OpenSession();
}
}
class Program
{
static void Main(string[] args)
{
using (var session = NHiberanteHelper.OpenSession())
{
using (var trans = session.BeginTransaction())
{
var account = new Account
{
Nick = "dfdwf",
Password = "xxx"
};
session.Save(account);
trans.Commit();
}
}
Console.ReadKey();
}
}
Problem is that this Fluent configuration always drop table in database.
I need only check if table doesnt exist so create table not always when code run drop table.

Answer 1

Your call to new SchemaExport(cfg).Create(true, true) is exporting the configuration to the database. This will drop and re-create it (it's not clever enough to work out the differences and just execute them.
You could use SchemaUpdate, which will update the schema instead. Here's a blog post about it: http://geekswithblogs.net/dotnetnomad/archive/2010/02/22/138094.aspx
I would always prefer to update tables myself or use something like Redgate's SQLCompare to update a schema whilst preserving data.