建立連接分為六步：
1.定義連接字符串，Oracle 的連接字符串為：

                        192.168.1.130:1521/mydata;Persist Security Info=True;User ID=em_test;PassWord=test123;Unicode=True";

2.根據(jù)連接字符串成連接
3.打開連接
4.實例命令對象
5.操作
6.關(guān)閉連接

看一個例子： 

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 OpenCloseDB
{
    public partial class Form1 : Form
    {
        public Form1()
        {             InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OracleConnection connection = null;
            int num = 0;
            string message = "";
            String sql = "select count(*) from ex_user";
            try
            {
                string connString = "Data Source=mydata;Persist Security Info=True;User ID=test;Password=huikk123;Unicode=True";

                // 創(chuàng)建connection對象
                connection = new OracleConnection(connString);

                // 打開連接
                connection.Open();
                OracleCommand command = new OracleCommand(sql, connection);
                num = int.Parse(command.ExecuteScalar().ToString());
                message = string.Format("共有{0}條用戶信息!", num);
                MessageBox.Show(message);
            }
            catch (Exception ex)
            {

                MessageBox.Show("出現(xiàn)異常"+ex.Message);
            }
            finally
            {
                if (connection != null)
                {
                    connection.Close();
                }
            }
        }
    }
}