private void button1_Click(object sender, EventArgs e)
        {
            //connect with database
            OleDbConnection connection = new OleDbConnection();
            connection.ConnectionString = @"Provider=""Microsoft.Jet.OLEDB.4.0"";Data Source=""demo.mdb"";User Id=;Password=";
            OleDbCommand command = new OleDbCommand();
            command.CommandText = "select * from parts where Cost<1000 and ListPrice>500";
            DataSet dataSet = new System.Data.DataSet();
            OleDbDataAdapter dataAdapter = new OleDbDataAdapter(command.CommandText, connection);
            dataAdapter.Fill(dataSet);
            DataTable dt = dataSet.Tables[0];
            this.dataGridView1.DataSource = dt;
            //export specific data to Excel
            Workbook book = new Workbook();
            Worksheet sheet = book.Worksheets[0];
            book.Worksheets[0].InsertDataTable(this.dataGridView1.DataSource as DataTable, true, 1, 1);
            book.SaveToFile("sample.xlsx", ExcelVersion.Version2010);
            System.Diagnostics.Process.Start("sample.xlsx");
        }