关于oracle的小问题求指教

 代码如下但是没有结果俺不执行只能执行到conn。open然后就跳到catch了求解求指教，先谢
 private void button1_Click(object sender, EventArgs e)
        {
            string str = "data source=sid;user=scott;password=tiger";
            OracleConnection conn = new OracleConnection(str);
            try
            {
                conn.Open();
                OracleCommand com = conn.CreateCommand();
                com.CommandText = "select * from scott.emp";
                OracleDataReader dr = com.ExecuteReader();
                while (dr.Read())
                {
                    this.textBox1.Text = dr.GetOracleString(0).ToString();
                }
                dr.Close();
            }
            catch
            {
                MessageBox.Show("error");
            }
            finally
            {
                conn.Close();
            }