I ve working in a project in which i must work with Access and SQL Server at the same time. Migrating data from one database to other. I try to find the way to work with both but i realize that if i change the web.config my application resets.
So i find a better way, but i am not sure if it is the best way. Here is the code if its useful for you much better.

public enum tipo
{
access = 1,
sql = 2
}

public ISession getSessionByTipo(tipo ti)
{
Configuration config = new Configuration();
IDictionary dir = new Hashtable() ;
string conn;
string dialect;
string driver;

if (ti == tipo.access)
{
conn = this.mdbConn;
dialect = this.mdbDialect;
driver = this.mdbDriver;
}
else
{
conn = this.sqlConn;
dialect = this.sqlDialect;
driver = this.sqlDriver;
}


foreach (DictionaryEntry de in config.Properties)
{
switch (de.Key.ToString())
{
case "hibernate.connection.connection_string":
dir.Add(de.Key.ToString(), conn);
break;
case "hibernate.connection.driver_class":
dir.Add(de.Key.ToString(), driver);
break;
case "hibernate.dialect":
dir.Add(de.Key.ToString(), dialect);
break;
case "hibernate.connection.provider":
dir.Add(de.Key.ToString(),"NHibernate.Connection.DriverConnectionProvider");
break;
}
}

config.Properties = dir;
config.AddAssembly("Business");

return config.BuildSessionFactory().OpenSession();

}

My usual solution to this is to actually have two different SessionFactory objects configured from different sections in the web.config. Each SessionFactory would be connected to different databases - one to Access, the other the SQL Server.

Then you can move the objects between the sessions for each SessionFactory by evicting from the source Session and then using SaveOrUpdate on the destination Session (depending on what you're trying to do, of course).

Cheers,

Symon.