Use
protected void Page_Load(object sender, EventArgs e)
{
string current_date = DateTime.Now.ToString("dd-MMM-yy");
Lbl_todays_date.Text = current_date;
string total_booked = "select count(selected_date) from user_record where selected_date='" + Lbl_todays_date.Text + "'";
cmd2 = new OleDbCommand(total_booked, cn);
dr2 = Convert.ToInt32(cmd2.ExecuteScaler());
cn.Close();
}