title: Fluent NHibernate Composite Mapping <long, string>
body: <p>I am having problems with mapping a particular table that has  as primary key.
  Let's say I have this table:</p>
  
  <pre><code>CREATE TABLE ALERT_EMAIL
  (
      IDALERT NUMBER(10, 0) NOT NULL,
      EMAIL   VARCHAR2(100 BYTE) NOT NULL,
      CONSTRAINT ALERT_EMAIL_PK PRIMARY KEY ( IDALERT , EMAIL ) ENABLE
  )
  </code></pre>
  
  <p>Here is my mapping:</p>
  
  <pre><code>public class AlertEmailMap : ClassMap&lt;AlertEmail&gt;
      {
          public AlertEmailMap()
          {
              Schema("XXX");
              Table("ALERT_EMAIL");
              CompositeId().KeyReference(x =&gt; x.Alert, "IDALERT").KeyReference(x =&gt; x.Email, "EMAIL");
          }
      }
  </code></pre>
  
  <p>I am getting this error: "An association from the table ALERT_EMAIL refers to an unmapped class: System.String"</p>
  
  <p>Is it because I have a string in my CompositeId?
  How can I map that table correctly?</p>
  
  <p>Thanks.</p>