AsyncCallBack Method Help Needed

class GetAllData
    {
        SqlConnection cnn = new SqlConnection("Data Source=DEVELOPER;Initial Catalog=ERPLiveDB;Integrated Security=True;Asynchronous Processing=True");
        SqlCommand cmd = new SqlCommand();
        DataTable tblResult = new DataTable();
        private static int counter = 0;
        protected ToolStripStatusLabel lblval;

        public DataTable GetByQuery(string Query, ref ToolStripProgressBar pb,ref ToolStripStatusLabel lbl)
        {
            cmd = cnn.CreateCommand();
            cmd.CommandText = Query;
            lblval = lbl;
            try
            {
                cnn.Open();
                AsyncCallback callback = new AsyncCallback(RetrieveDataCallback);
                           
                
                cmd.BeginExecuteReader(callback, cmd,CommandBehavior.CloseConnection);
                //show status of processing in progress bar. 
                while (counter < 1)
                {
                    lbl.Text = pb.Value.ToString() + " %" + "Retrieved.";
                    if (pb.Value != 100)
                    {
                        pb.Value += 2;
                    }
                    else
                    {
                        pb.Value = 0;
                        //lbl.Text = "";
                    }
                    Thread.Sleep(50);
                    lbl.Text = pb.Value.ToString() + " %" + "Retrieved.";
                }
                pb.Value = 100;
                
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
            finally
            {
                cnn.Close();
            }
            return (tblResult);
        }
        private void RetrieveDataCallback(IAsyncResult result)
        {
            SqlDataReader dr = null;
            try
            {
                SqlCommand comm = (SqlCommand)result.AsyncState;
               
                dr = comm.EndExecuteReader(result);
                //while (dr.Read())
                //{
                //    lblval.Text = lblval.Text + ".";
                //}
                //tblResult.Load(dr, LoadOption.OverwriteChanges);
                tblResult.Load(dr);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
            finally
            {
                try
                {
                    if (!dr.IsClosed)
                    {
                        dr.Close();
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message.ToString());
                }
                Interlocked.Increment(ref counter);
            }
        }
    }