NHibernate的问题，用过的人来帮忙

web.config<configSections>
<section name="nhibernate" type="System.Configuration.NameValueSectionHandler,System,Version=1.0.5000.0,Culture=neutral, PublicKeyToken=b77a5c561934e089" />
<!--section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" /-->
</configSections>
<!-- log4net (required by NHibernate) and other app specific config follows -->
<nhibernate>
<add key="hibernate.connection.provider" value="NHibernate.Connection.DriverConnectionProvider" />
<add key="hibernate.connection.isolation" value="ReadCommitted" />
<!--add key="hibernate.connection.driver_class" value="NHibernate.Driver.SqlClientDriver" />
<add key="hibernate.connection.connection_string" value="data source=.;user id=sa;initial catalog=fore;password=123456" />
<add key="hibernate.dialect" value="NHibernate.Dialect.MsSql2000Dialect" /-->
<add key="hibernate.connection.driver_class" value="NHibernate.Driver.OracleClientDriver" />
<add key="hibernate.connection.connection_string" value="data source=fore;user id=sa;password=123456" />
<add key="hibernate.dialect" value="NHibernate.Dialect.OracleDialect" />
</nhibernate>f_module.hbm.xml<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="F_Module" assembly="YiWan.Domain">
<class name="YW.Domain.Entity.Module.F_Module,YW.Domain" table="F_Module">
<id name="modCode" column="ModCode" type="Int32" length="32">
<generator class="assigned" />
</id>
<property name="rootCode" column="rootCode" type="String" length="32" />
<property name="parentCode" column="parentCode" type="String" length="32" />
<property name="modName" column="modName" type="String" length="32" />
<property name="modValue" column="modValue" type="String" length="32" />
<property name="modPath" column="modPath" type="String" length="32" />
</class>
</hibernate-mapping>cs代码
Configuration cfg  = new Configuration()
.AddAssembly("YW.Domain");

ISessionFactory factory = cfg.BuildSessionFactory();
ISession session = factory.OpenSession();
ITransaction tf = session.BeginTransaction();
F_Module f = new F_Module("11111","ss"); session.Save(f); //session.Delete(f);
//NHibernate.Driver.OracleDataClientDriver

tf.Commit();
session.Flush();
session.Close();
～～～～～～～～～～～～～～～～～～～
我在sql server下调试成功
但是改变方言后使用oracle  提示ORA-12704: 字符集不匹配 
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.Data.OracleClient.OracleException: ORA-12704: 字符集不匹配