Question

I have some data, and I update it in a task: The app is a hack at the moment for an idea so apologies for the code.

Task.Factory.StartNew(() =>
    {
        dataGridView1.BeginInvoke((Action)(() =>
            {
                dataGridView1.SuspendLayout();
            }));

        dataSet1.Reset();
        da.Fill(dataSet1);

        dataGridView1.BeginInvoke((Action)(() =>
            {
                dataGridView1.DataSource = dataSet1.Tables[0];
                dataGridView1.Columns[0].Visible = false;
                dataGridView1.Columns[1].Width = 50;
                dataGridView1.ResumeLayout();
            }));
    }
    ).ContinueWith(task =>
        {
            if (dataSet1.Tables[0].Rows.Count > 0)
            {
                if (lastcount != dataSet1.Tables[0].Rows.Count)
                {
                    lastcount = dataSet1.Tables[0].Rows.Count;
                    if (lastcount == 0)
                    {
                        NotifyWithMessage("The items have been cleared", "Items cleared");
                    }
                    else
                    {
                        NotifyWithMessage(String.Format("There are {0} new items in your monitor", dataSet1.Tables[0].Rows.Count));
                    }
                }
            }
        }
    );

Now, the code fundamentally works. No errors, which is nice..

When it was updated outside a task, there was no flashing of the datavgridview at all, when I run it in debug, it’s very minor and well within acceptable for the hack.. the moment I run it outside debugging… it’s terribly obvious! The suspend and resume layouts have not made any difference at all. I need the code in the thread, because the UI is lumpy responsive without – whereas it’s acceptable, but it has the bad refresh now.

My Datagridview is custom coloured depending on cell colours, but, I just cant see why there’s the difference between debug and release, I’d expect the performance the other way round!

(I tried Invoke and BeginInvoke…)

I looked at Horrible redraw performance of the DataGridView on one of my two screens

And under debug, this doesn’t flicker at all, not even a bit… Under release conditions, there is a ridiculous flicker…

What can I do?

Answer 1

In the end heres what I did:
I rean the query into a new dataset, if the count was the same, then I didnt update the grid, if the count had changed I did.

timer1.Stop();

        Task<Boolean>.Factory.StartNew(() =>
            {
                DataSet t = new DataSet();
                //_dataSet1.Reset();
                Boolean ok = false;
                Int16 retries = 0;
                while (!ok && retries<3)
                try
                {
                    da.Fill(t);
                    ok = true;
                }
                catch
                {
                    retries++;
                    Thread.Sleep(1000);
                }
                //if (!ok) throw new Exception("DB error");
                if (!ok) return false;
                try
                {
                    if (t.Tables.Count > 0 && t.Tables[0].Rows.Count != _lastcount)
                    {
                        _dataSet1 = t;
                        _lastcount = t.Tables[0].Rows.Count;
                        return true;
                    }
                }
                catch {  }
                return false;
            }).ContinueWith(task =>
                {
                    if (task.IsFaulted)
                    {
                        SQLFailed();
                        return;
                    }
                    if (!task.Result) return;


                    Invoke((Action) (() =>
                                         {
                                             dataGridView1.DataSource = _dataSet1.Tables[0];
                                             dataGridView1.Columns[0].Visible = false;
                                             dataGridView1.Columns[1].Width = 50;
                                         }));

                    if (_lastcount == 0)
                    {
                        NotifyWithMessage("The items have been cleared", "Items cleared");
                    }
                    else
                    {
                        NotifyWithMessage(String.Format("There are {0} new items in your monitor", _lastcount));
                    }
                });


    timer1.Start();