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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.

C#代码

1. /// <summary>
2. /// This service is designed to return a TaskScheduler for application’s main, UI thread.
3. /// This service MUST be instantiated on UI thread.
4. /// </summary>
5. [DebuggerNonUserCode]
6. public class UITaskSchedulerService : IUITaskSchedulerService
7. {
8. private static readonly UITaskSchedulerService InstanceField = new UITaskSchedulerService();
9. private static readonly TaskScheduler TaskSchedulerUI;
10. private static readonly Thread GuiThread;
12. static UITaskSchedulerService()
13. {
14. GuiThread = Thread.CurrentThread;
15. TaskSchedulerUI = TaskScheduler.FromCurrentSynchronizationContext();
16. }
18. /// <summary>
19. /// Gets the instance.
20. /// </summary>
21. public static UITaskSchedulerService Instance
22. {
23. get
24. {
25. return InstanceField;
26. }
27. }
29. /// <summary>
30. /// Get TaskScheduler to schedule Tasks on UI thread.
31. /// </summary>
32. /// <returns>TaskScheduler to schedule Tasks on UI thread.</returns>
33. public TaskScheduler GetUITaskScheduler()
34. {
35. return TaskSchedulerUI;
36. }
38. /// <summary>
39. /// Check whether current tread is UI tread
40. /// </summary>
41. /// <returns><c>true</c>if current tread is UI tread.</returns>
42. public bool IsOnUIThread()
43. {
44. return GuiThread == Thread.CurrentThread;
45. }
46. }

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.

C#代码

1. Task.Factory
2. .StartNew(
3. () =>
4. _riskProvider.GetRiskPnL(),
5. CancellationToken.None,
6. TaskCreationOptions.None,
7. TaskScheduler.Default)
8. .ContinueWith(
9. (task) => ProcessResults(task.Result),
10. UITaskSchedulerService.Instance.GetUITaskScheduler()
11. )
12. //.ContinueWith(
13. // (task) => ProcessResults(task.Result),
14. // TaskScheduler.FromCurrentSynchronizationContext())
15. .LogTaskExceptionIfAny(Log)
16. .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

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