Sử dụng class System.Data.OracleClient

Oracle_ConnectString để trong file . config

nếu là web thì là web.config, nếu là app thì là app.config hoặc app.exe.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="Oracle_ConnectString" value="Data Source=dbtest;User ID=haitest;Password=hahaha;"/>
</appSettings>
</configuration>

using System.Data.OracleClient;

private void btnTestConnect_Click(object sender, EventArgs e)
{
   try 
   {
      string connectionString = ConfigurationSettings.AppSettings["Oracle_ConnectString"];
      OracleConnection myConnection = new OracleConnection(connectionString); 
      myConnection.Open();
      MessageBox.Show("Connected Sucessfully!","Connection Information");
   }
   catch (Exception ex)
   {
      MessageBox.Show(ex.Message,"Connection error");
   }
}