Скачать или смотреть Resolving WPF Windows Not Responding After Windows Sleep/Resume

A detailed guide on solving the issue of WPF applications becoming unresponsive after Windows sleeps and resumes. Find out the steps and insights to troubleshoot this common problem.
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This video is based on the question https://stackoverflow.com/q/69666153/ asked by the user 'Rich G' ( https://stackoverflow.com/u/16096720/ ) and on the answer https://stackoverflow.com/a/69676445/ provided by the user 'Rich G' ( https://stackoverflow.com/u/16096720/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem

Have you ever noticed that your WPF application becomes unresponsive after your Windows system wakes from sleep or suspend? This can be frustrating, especially if you rely on this application for timely notifications or events. A common scenario involves applications that run in the background and interact with the user through visible windows. In this guide, we will thoroughly explore a specific case—where a C- WPF application becomes non-interactive post-sleep/resume—and provide effective solutions to fix it.

Problem Overview

In a typical WPF application setup, one window handles background operations (let's call it the hidden window) while another displays interactive elements (the visible window). After a sleep or suspend state, issues arise:

The visible window fails to respond when activated.

The hidden window continues to function, leading to event handling accumulating.

This can hinder user experience and may require forceful application termination to regain control.

In-Depth Investigation

Application Structure

The application in question integrates several components:

Hidden Window: Conducts background tasks such as managing timers and handling notifications.

Visible Window: Displays event messages and interacts with users.

The application code utilizes the SystemEvents class to capture power mode changes, invoking processes when transitioning between sleep and active states.

[[See Video to Reveal this Text or Code Snippet]]

Identifying the Culprit

After thorough debugging—commenting out sections of the code—an underlying issue was discovered:

[[See Video to Reveal this Text or Code Snippet]]

This line, which was embedded deep within the hidden window's logic, created unintended side effects post-resume. Ultimately, it caused UI operations to be ignored, leaving the visible window frozen.

Solution to the Problem

To effectively resolve this WPF responsiveness issue after sleep, follow these steps:

1. Restructure Event Listeners

Ensure that all listeners for SystemEvents are managed at the application level rather than nested within a specific window’s code. This involves moving the session switch event handler out of the hidden window. Here is how you can rearrange your code:

[[See Video to Reveal this Text or Code Snippet]]

2. Test the Application

Once you have relocated the event handlers:

Run tests to confirm that the visible window responds as expected after resume.

Check for any additional events that may not have been handled properly during sleep/resume and rectify those if they exist.

3. Debug Any Remaining Issues

After restructuring, new issues might surface. Continue to debug these to ensure a seamless user experience. Areas to focus on may include:

Timer resets

State management of windows upon activation/deactivation

Conclusion

If your WPF application becomes unresponsive following a system suspend/resume, consider re-evaluating where you are placing your event listeners. By relocating any SystemEvents listeners to the application level, you can eliminate the unresponsiveness of your visible window and ensure smooth operation.

By following the principles discussed in this guide, not only can you troubleshoot your specific application issue effectively, but you will also enhance your understanding of handling multi-window scenarios in WPF applications.

If you have any questions or need further assistance, feel free to drop a comment below. Happy coding!