用OracleDataAdapter update dataset, code 如下：

DataSet ds_list = new DataSet();
OracleConnection Conn = new OracleConnection(CONN_STRING);
OracleDataAdapter da_mytable = new OracleDataAdapter();

string sql_mytable = "select * from mytable";

da_mytable.SelectCommand = new OracleCommand(sql_mytable, Conn);

OracleCommandBuilder cb_entity = new OracleCommandBuilder(da_entity);

Conn.Open();

da_mytable.Fill(ds_list, "mytable");

//modify data in ds_list.Tables["mytable"] with some French Character such as Montréal

da_mytable.Update(ds_list, "mytable");

Conn.Close();

问题：英文完全没问题，法文不行Montréal变成Montreal了，以前在SQL Server用过类似的code，没有问题，可能是Oracle与.Net dataadapter之间的兼容问题，有没有什么设置可以解决这个问题？

Thanks.