using System;
using System.Data;
using System.Data.OleDb;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            OleDbConnection connection ;
            OleDbDataAdapter oledbAdapter ;
            DataSet ds = new DataSet();
            int i = 0;
            connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Your mdb filename;";
            connection = new OleDbConnection(connetionString);
            try
            {
                connection.Open();
                oledbAdapter = new OleDbDataAdapter("select * from users", connection);
                oledbAdapter.Fill(ds);
                oledbAdapter.Dispose();
                connection.Close();
                for (i = 0; i <= ds.Tables[0].Rows.Count - 1; i++)
                {
                    MessageBox.Show (ds.Tables[0].Rows[i].ItemArray[0].ToString ());
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
    }
}