Warming up NHibernate succinctly

Following is a piece of code from the previous chapter that I had asked you to ignore then:

using System;
using NHibernate;
using NHibernate.Cfg;
using NHibernate.Dialect;
using NHibernate.Driver;
using NHibernate.Tool.hbm2ddl;
using Environment = NHibernate.Cfg.Environment;

namespace Tests.Unit
{
  public class InMemoryDatabaseForXmlMappings : IDisposable
  {
    protected Configuration config;
    protected ISessionFactory sessionFactory;
    public ISession Session;
    public InMemoryDatabaseForXmlMappings()
    {
      config = new Configuration()
      .SetProperty(Environment.ReleaseConnections, "on_close")
      .SetProperty(Environment.Dialect, typeof
      (SQLiteDialect).AssemblyQualifiedName)
      .SetProperty(Environment.ConnectionDriver, typeof
      (SQLite20Driver).AssemblyQualifiedName)
      .SetProperty(Environment.ConnectionString, "data
      source=:memory:")
      .AddFile("Mappings/Xml/Employee.hbm.xml&quot...