Creating a SQLite Database Using NHibernate, But Only Once

Question

I read a few examples on how to use NHibernate with SQLite, and most of them relate to CRUD operations with unit testing and all that. So, the examples that I have encountered and followed so far are related to this. This is good, but the problem is that every time I run my program, the database is recreated! How can I change my code so that if the database already exists, NHibernate will NOT create it? And yes, I tried to check with File.Exists, but it ignored; I believe it because NHibernate gets to the file first.

This is my mapping:

<?xml version="1.0" encoding="utf-8" ?> <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2"> <session-factory name="NHibernate.Test"> <property name="connection.driver_class">NHibernate.Driver.SQLite20Driver</property> <property name="dialect">NHibernate.Dialect.SQLiteDialect</property> <property name='proxyfactory.factory_class'>NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu</property> <property name="query.substitutions">true=1;false=0</property> <property name="show_sql">false</property> </session-factory> </hibernate-configuration> 

And my complete code:

 using System; using System.Collections.Generic; using System.Data.SQLite; using System.Linq; using NHibernate; using NHibernate.Cfg; using PruebaNHLite.Domain; namespace PruebaNHLite { public class Program { public static ISession sess; public static Configuration cfg; public static SQLiteConnection connection; private const string CONNECTION_STRING = @"Data Source=nhlite.db;Pooling=true;FailIfMissing=false; BinaryGUID=false;New=false;Compress=true;Version=3"; static void Main(string[] args) { Init(); BuildSchema(); Insert(); Retrieve(); sess.Close(); sess = null; } public static void Init() { // Initialize NHibernate cfg = new Configuration(); cfg.Configure(); IDictionary<string, string> props = new Dictionary<string, string>(); props.Add("connection.connection_string", CONNECTION_STRING); props.Add("connection.driver_class", "NHibernate.Driver.SQLite20Driver"); props.Add("dialect", "NHibernate.Dialect.SQLiteDialect"); props.Add("proxyfactory.factory_class", "NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu"); props.Add("query.substitutions", "true=1;false=0"); props.Add("show_sql", "false"); cfg.SetProperties(props); cfg.AddAssembly(typeof(Person).Assembly); connection = new SQLiteConnection(CONNECTION_STRING); connection.Open(); // Get ourselves an NHibernate Session var sessions = cfg.BuildSessionFactory(); sess = sessions.OpenSession(); } private static void BuildSchema() { NHibernate.Tool.hbm2ddl.SchemaExport schemaExport = new NHibernate.Tool.hbm2ddl.SchemaExport(cfg); schemaExport.Execute(false, true, false, connection, null); } public static void Insert() { // Create a Person... var person = new Person { Name = "Almudena", Surname = "Pamplinas", Age = 5 }; // And save it to the database sess.Save(person); sess.Flush(); } public static void Retrieve() { IQuery q = sess.CreateQuery("FROM Person"); foreach (var p in q.List().Cast<Person>()) { Console.WriteLine(string.Format("{0} {1}, de {2} años.", p.Name, p.Surname, p.Age)); } Console.ReadLine(); } } } 

Answer 1

Try using SchemaUpdate instead of SchemaExport . SchmaExport will delete all tables, restrictions, etc. And recreates them. SchemaUpdate will just update your db. However, I caution against using SchemaUpdate / SchemaExport in a production environment, as these are not tools for migrating product quality.