Refreshing gridview with new data

Hi...

 try.. celect change event..

         private void search_d()
        {
          

            if (connectiondb.State == ConnectionState.Closed)
            {
                connectiondb.Open();
            }
            //Select_sub_or_date_for_result frm = new Select_sub_or_date_for_result();
            string all_data_query = "Select Main_id,SName,Mrk_R,Mrk_W,mark from tbl_result where sub='" + comboBox2.Text.Trim() + "' and Exam_date='" + dateTimePicker2.Text + "' ";
            com = new OleDbCommand(all_data_query, connectiondb);
            com.CommandType = CommandType.Text;
            OleDbDataAdapter da = new OleDbDataAdapter(com);
            DataTable dt = new DataTable();
            da.Fill(dt);
            this.dataGridView1.DataSource = dt;
            connectiondb.Close();
        }