How to Update a ProgressBar Continuously Using a BackgroundWorker?

Correctly implement the use of background worker threads to update the progress bar

Background:

The

BackgroundWorker class is a component used to perform long-running tasks in the background while keeping the UI responsive. It allows you to update the UI or perform any other operation that needs to be performed on the UI thread.

Question:

A user attempts to implement a BackgroundWorker to update the progress bar while a long-running task is executing. However, the progress bar animation doesn't start until the DoWork thread completes. The user also tried using another BackgroundWorker to update the progress bar, but it still didn't work until the first BackgroundWorker 's DoWork thread completed.

Answer:

To correctly use BackgroundWorker to update the progress bar, you need:

1. Implement BackgroundWorker correctly: Make sure that BackgroundWorker's WorkerReportsProgress property is set to true and that the ProgressChanged event handler is implemented to update the progress bar.
2. Call ReportProgress in the DoWork method: In the BackgroundWorker's DoWork event handler, call the ReportProgress method at appropriate intervals to report the current progress of the task. This will trigger the ProgressChanged event and update the progress bar on the UI thread.
3. Update the progress bar on the UI thread: The ProgressChanged event is raised on the UI thread, so UI elements can be updated directly from this event handler. Here you can update the progress bar's Value attribute to reflect the reported progress.

Code example:

Here is a simple code example demonstrating how to use BackgroundWorker to update a progress bar:

// 用户控件代码隐藏
private void DoWork(object sender, DoWorkEventArgs e)
{
    for (int i = 0; i <= 100; i++)
    {
        // 模拟长时间运行的工作
        Thread.Sleep(100);
        backgroundWorker.ReportProgress(i);
    }
}

private void ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    // 当调用 ReportProgress 方法时，这会在 UI 线程上调用
    progressBar.Value = e.ProgressPercentage;
}

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