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

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

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            OleDbConnection cnn ;
            OleDbCommand cmd ;
            string sql = null;

            connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=Your mdb filename;";
            sql = "Your SQL Statement Here like Select Count(*) from product"; 

            cnn = new OleDbConnection(connetionString);
            try
            {
                cnn.Open();
                cmd = new OleDbCommand(sql, cnn);
                Int32 count = Convert.ToInt32(cmd.ExecuteScalar());
                cmd.Dispose();
                cnn.Close();
                MessageBox.Show (" No of Rows " + count);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }
    }
}