Task Schedulers

1. 1.   What is a TaskScheduler?

 

A TaskScheduler represents an object that handles the low-level work of scheduling threads. The Framework provides two concrete implementations: the default scheduler which works in tandem with ThreadPool and the synchronization context scheduler, which is used by WPF and WinForms. Which task scheduler a task should use we can point out manually.

public partial class Form1 : Form

{

private readonly TaskScheduler _taskScheduler = null;

private CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();

public Form1()

{

    InitializeComponent();

    Text = “some text”;

    Width = 500;

    Height = 200;

    Visible = true;

    _taskScheduler = TaskScheduler.FromCurrentSynchronizationContext();

}

private void InitializeComponent(){}

private int DoSomeCalc(int n)

{

    for (int i = 0; i < n; i++)

    {

        Thread.Sleep(100);

        n++;

    }

    return n;

}

protected override void OnMouseClick(MouseEventArgs e)

{

    if (_cancellationTokenSource != null)

    {

        _cancellationTokenSource.Cancel();

        _cancellationTokenSource = null;

    }

    else

    {

        _cancellationTokenSource = new CancellationTokenSource();

        Task<int> task = new Task<int>(() => DoSomeCalc(10), _cancellationTokenSource.Token);

        task.Start();

        task.ContinueWith(t => { Text = “Thread completed, the result is: ” + t.Result.ToString(); }, CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, _taskScheduler);

        task.ContinueWith(t => { Text = “Thread was canceled, the result is: ” + t.Result.ToString(); }, CancellationToken.None, TaskContinuationOptions.OnlyOnCanceled, _taskScheduler);

        task.ContinueWith(t => { Text = “Thread faulted, the result is: ” + t.Result.ToString(); }, CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, _taskScheduler);

    }

    base.OnMouseClick(e);

}

}

It’s possible to write our own TaskScheduler.