C#

task Scheduler根据定义

The task Scheduler by the definition blurb.

“Is the class where the usage context is within the task libraries. “

它的作用像是WPF/Winform时代的SynchronizationContext.

It is like the Synchronization context in the cross WPF/Win forms era.

像SynchronizationContext.一样，TaskScheduler也有可能依赖特定的UI SynchronizationContext.

As with the Synchronization context, we may have requirement for like the UI context synchronization.

代码如下:

Give the code as below.

/// <summary>
/// This service is designed to return a TaskScheduler for application's main, UI thread.
/// This service MUST be instantiated on UI thread.
/// </summary>
[DebuggerNonUserCode]
public class UITaskSchedulerService : IUITaskSchedulerService
{
    private static readonly UITaskSchedulerService InstanceField = new UITaskSchedulerService();
    private static readonly TaskScheduler TaskSchedulerUI;
    private static readonly Thread GuiThread;

    static UITaskSchedulerService()
    {
        GuiThread = Thread.CurrentThread;
        TaskSchedulerUI = TaskScheduler.FromCurrentSynchronizationContext();
    }

    /// <summary>
    /// Gets the instance.
    /// </summary>
    public static UITaskSchedulerService Instance
    {
        get
        {
            return InstanceField;
        }
    }

    /// <summary>
    /// Get TaskScheduler to schedule Tasks on UI thread.
    /// </summary>
    /// <returns>TaskScheduler to schedule Tasks on UI thread.</returns>
    public TaskScheduler GetUITaskScheduler()
    {
        return TaskSchedulerUI;
    }

    /// <summary>
    /// Check whether current tread is UI tread
    /// </summary>
    /// <returns><c>true</c>if current tread is UI tread.</returns>
    public bool IsOnUIThread()
    {
        return GuiThread == Thread.CurrentThread;
    }
}

该class的要求是必须在UI thread初始化。

The requirement for the UITaskShcedulerService is that you should construct the singleton instance to start from a UI threads.

因为他内部使用的是TaskScheduler.FromCurrentSynchronizationContext，根据MSDN的TaskScheduler Class 定义 ，它拿到的是当前thread的synchronization context

Because it  internally use the TaskScheduler.FromCurrentSynchronizationContext. and from the TaskScheduler Class from MSDN, it retrieve the current thread’s synchronization context.

Task.Factory
                .StartNew(
                    () =>
                    _riskProvider.GetRiskPnL(),
                    CancellationToken.None,
                    TaskCreationOptions.None,
                    TaskScheduler.Default)
                  .ContinueWith(
                    (task) => ProcessResults(task.Result),
                    UITaskSchedulerService.Instance.GetUITaskScheduler()
                    )
                //.ContinueWith(
                // (task) => ProcessResults(task.Result),
                // TaskScheduler.FromCurrentSynchronizationContext())
                .LogTaskExceptionIfAny(Log)
                .ContinueWith(x => DataUpdater());

 处理结果需要dispatch到UI thread上，这样才能正确的显示。

We need to dispatch the process result back to the UI thread so that display can be properly handled.

References:

TaskScheduler Class