Answer 1

您仍然在模型中映射了外键（HeaderID）。你应该将HeaderID或Header作为属性，但不能同时作为属性。

从模型中删除它：

public class POSErrorQueueDetail
{
    public virtual Int32 DetailID { get; set; }
    public virtual POSErrorQueue Header { get; set; }
}

要访问HeaderID，只需访问Header.HeaderID即可。和映射：

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="TPMControlPanel" namespace ="TPMControlPanel.Models">
  <class name="POSErrorQueueDetail" table="POSErrorQueueDetails">
    <id name="DetailID">
      <generator class="identity" />
    </id>
    <!--all other property mappings removed for brevity -->
    <many-to-one name="Header" class="POSErrorQueue" column="HeaderID" fetch="join" />
  </class>
</hibernate-mapping>