Best practices for using the thread pool (XAML)

Article
09/15/2015

[This article is for Windows 8.x and Windows Phone 8.x developers writing Windows Runtime apps. If you’re developing for Windows 10, see the latest documentation]

This topic describes best practices for working with the thread pool.

Do's

Use the thread pool to do parallel work in your app.
Use work items to accomplish extended tasks without blocking the UI thread.
Create work items that are short-lived and independent. Work items run asynchronously and they can be submitted to the pool in any order from the queue.
Dispatch updates to the UI thread with the Windows.UI.Core.CoreDispatcher.
Use ThreadPoolTimer.CreateTimer instead of the Sleep function.
Use the thread pool instead of creating your own thread management system. The thread pool runs at the OS level with advanced capability and it is already optimized.
In C++, ensure that work item delegates use the agile threading model (C++ delegates are agile by default).
Use pre-allocated work items for critical asynchronous work.

Dont's

Don't create periodic timers with a period value of <1 millisecond (including 0). This will cause the work item to behave as a single-shot timer.
Don't submit periodic work items that take longer to complete than the amount of time you specified in the period parameter.
Don't do any extensive work in the UI dispatch handler. The handler provided to the UI core dispatcher runs in the UI thread.
Don't try to send UI updates (other than toasts and notifications) from a work item running in a background task. Instead, use background task progress and completion handlers - for example, IBackgroundTaskInstance.Progress.
Don't try to create work item handlers that use the async keyword. Such handlers can cause unexpected behavior by running the work item in a thread other than the one that the thread pool assigns. For example, completion handlers will run before the work item completes.
Don't try to run a pre-allocated work item more than once without reinitializing it.