我得到错误：nhibernate无法编译映射文件

Question

我的源代码是：

var cfg = new Configuration();
cfg.DataBaseIntegration(x =>
{
   x.ConnectionString = "......";
   x.Driver<SqlClientDriver>();
   x.Dialect<MsSql2008Dialect>();
});
cfg.AddAssembly(Assembly.GetExecutingAssembly());
var sessionFactory = cfg.BuildSessionFactory(); //builds meta data and mapping

using (var session = sessionFactory.OpenSession())
using (var tx = session.BeginTransaction()) {
   var customers = session.CreateCriteria<Customer>()
                          .List<Customer>();
   foreach (var customer in customers) {
      Console.WriteLine("{0} {1}", customer.FirstName, customer.LastName);
   }
   tx.Commit();
}

我的映射文件Customer.hbm.xml是：

<?xml version="1.0" encoding="utf-8" ?> 
<hibernate-mapping xmlns="urn:hibernate-mapping-2.2" assembly="ConsoleApplication1" namespace="ConsoleApplication1">
  <class name="Customer">
    <id name="Id">
      <generator class="native"/>
    </id>
    <property name="FirstName"/>
    <property name="LastName"/>
  </class>
</hibernate-mapping>

我收到错误： nhibernate无法编译映射文件

有人知道为什么吗？