string strConn = "Provider=MSDAORA;Data Source=" + textBox3.text + ";User Id=" + textBox1.text + ";Password=" + textBox2.text + ";";
            OleDbConnection conn = new OleDbConnection(strConn);
            OleDbCommand command = new OleDbCommand(SQL, conn);
            try
            {
                // connection.Open();
                conn.Open();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Подключение не удалось: " + ex.Message);

            }

            OleDbDataReader reader = command.ExecuteReader();

            while (reader.Read())
            {
                MessageBox.Show(reader.GetString(0) + ", " + reader.GetString(1));
            }

            reader.Close();

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Windows.Forms;
using System.Data.OleDb;
using System.Data;
namespace dsp
{
    static class Program
    {
        /// <summary>
        /// Главная точка входа для приложения.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Logon());
        }
       static public OleDbConnection;

    }
}

    static class Program
    {
        static public OleDbConnection conn { set; get; }
        /// <summary>
        /// Главная точка входа для приложения.
        /// </summary>
        [STAThread]
       
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Logon());
          
            string strConn = "Provider=MSDAORA;Data Source=testodb;User Id=kak;Password=ft6yhgy7;";
            conn = new OleDbConnection(strConn);
            try
            {
                conn.Open();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Подключение не удалось: " + ex.Message);
            }
        }
   
      
        }
 }

        private void button1_Click(object sender, EventArgs e)
        {
          string  SQL = "SELECT * FROM smr";
           OleDbCommand command = new OleDbCommand(SQL, Program.conn);
            MessageBox.Show("OK");
                  OleDbDataReader reader = command.ExecuteReader();

    static class Program
    {
        static public OleDbConnection conn { set; get; }
        /// <summary>
        /// Главная точка входа для приложения.
        /// </summary>
        [STAThread]
       
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Logon());
          
            string strConn = "Provider=MSDAORA;Data Source=testodb;User Id=kak;Password=xxx;";
            conn = new OleDbConnection(strConn);
            try
            {
                conn.Open();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Подключение не удалось: " + ex.Message);
            }
        }
   
      
        }
 }

        private void button1_Click(object sender, EventArgs e)
        {
          string  SQL = "SELECT * FROM smr";
           OleDbCommand command = new OleDbCommand(SQL, Program.conn);
            MessageBox.Show("OK");
                  OleDbDataReader reader = command.ExecuteReader();