public void ReadMyData(string connectionString)
{
    string queryString = "SELECT OrderID, CustomerID FROM Orders";
    using (OleDbConnection connection = new OleDbConnection(connectionString))
    {
        OleDbCommand command = new OleDbCommand(queryString, connection);
        connection.Open();
        OleDbDataReader reader = command.ExecuteReader();

        while (reader.Read())
        {
            Console.WriteLine(reader.GetInt32(0) + ", " + reader.GetString(1));
        }
        // always call Close when done reading.
        reader.Close();
    }
}

//引入命名空间
using System;
using System.Data;
using System.Data.OleDb;

class MainClass
{
  [STAThread]
  static void Main(string[] args)
  {
    string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\\Northwind.mdb";
    string SQL = "SELECT * FROM Orders";

    OleDbConnection conn = new OleDbConnection(ConnectionString);

    OleDbCommand cmd = new OleDbCommand(SQL);
    cmd.Connection = conn;

    conn.Open();

    OleDbDataReader reader = cmd.ExecuteReader();

    while (reader.Read()) 
    {
      Console.Write("OrderID:"+reader.GetInt32(0).ToString() );
      Console.Write(" ,");
      Console.WriteLine("Customer:" + reader.GetString(1).ToString() );
    }
    reader.Close();
    conn.Close();
  }
}