Windows Form UI Update issue with Task in C#

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We are working on a windows application which caters to an engineering calculation which are essentially very long running. So we are basically trying to keep the calculation module separate and working in a separate worker thread and pass it an Action delegate in method signature which will be invoked to report the calculation progress in the UI. The delegate handler declared in the UI will be updating the UI. We found that while a huge loop is running in the calculation, the UI is not showing the periodic progress and only displaying the final result. If a Thread Sleep for 1 millisecond is introduced in the calculation loop, the UI is getting updated correctly. This is not expected behavior as we are executing the calculation using a separate Task and updating the UI using BeginInvoke calls.

I have created a simple application to demonstrate our approach and code so that it is easier to understand. It is obvious that we are missing something very simple but cannot quite pin it down. Will appreciate any insights.

Thanks for reading.

private void cmdStart_Click(object sender, EventArgs e)
    {
        txtResultDIsplay.Text = "";
        var maxIterations = long.Parse(txtIterationNo.Text.Trim());

        var ui = TaskScheduler.FromCurrentSynchronizationContext();
        Task<double> calculationTask = Task.Factory.StartNew<double>(() => SumRootN(maxIterations, UpdateProgress));
        var handleResultTask = calculationTask.ContinueWith((t) => DisplayResult(t),
                    CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, ui);
    }

---

private void DisplayResult(Task<double> calculationTask)
        {
            txtResultDIsplay.Text = "Final Calculation Result : " + calculationTask.Result.ToString();
        }

---

private void UpdateProgress(string msg)
    {
        this.BeginInvoke((MethodInvoker)delegate
        {
            txtResultDIsplay.Text = msg;
        });
    }

---

public double SumRootN(long maxIterations, Action<string> progressUpdateDelegate)
    {
        int root = 20;
        double result = 0;
        for (long i = 1; i < maxIterations; i++)
        {
            Thread.Sleep(1);
            result += Math.Exp(Math.Log(i) / root);
            progressUpdateDelegate(result.ToString("0.00000"));
        }
        return result;
    }

asked 2 mins ago

koder

313

Windows Form UI Update issue with Task in C#