C#远程连接oracle数据库，以下是源代码，另外，本机未安装oracle客户端，运行后提示错误，求高手们解决

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OracleClient;

namespace 连接远程oracle
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connstring = "Data Source=(DESCRIPTION=" + "(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=IP)(PORT=1521)))" + "User ID=scott;Password=tiger;";
            OracleConnection conn = new OracleConnection(connstring);
            try
            {
                conn.Open();
                OracleCommand cmd = conn.CreateCommand();
                cmd.CommandText = "select * from emp";
                OracleDataReader odr = cmd.ExecuteReader();
                while (odr.Read())
                {
                    textBox1.Text = "远程数据库时间:" + odr.GetOracleDateTime(0).ToString();
                    textBox1.Text = textBox1.Text  + "远程数据库时间:" + odr.GetString(2);
                }
                odr.Close();
            }
            catch
            {
                MessageBox.Show("erro");
            }
            finally
            {
                conn.Close();
            }
   
        }
    }
}

追问：HOST=IP，其中的IP是远程数据的IP地址，我把客户端也安装上了，和服务器的版本是一样的，PLSQL Developer可以正常连接（主机字符串用“IP:1521/orcl”），在tnsnames.ora中也添加了如下文字：
ORCL =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = IP)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = orcl)
)
)
程序运行时调用了MessageBox.Show("erro");语句，显示"erro"提示。