WinForms Application: Unexpected Behavior with BackgroundWorker Progress Reporting on UI Thread
I've looked through the documentation and I'm still confused about I'm facing an issue with the `BackgroundWorker` in my WinForms application. I have a long-running task that I need to execute on a separate thread, and I'm using the `ProgressChanged` event to report progress back to the UI. However, it seems that sometimes the UI does not update as expected when I call `ReportProgress`. Here’s the relevant part of my code: ```csharp private void btnStart_Click(object sender, EventArgs e) { BackgroundWorker worker = new BackgroundWorker(); worker.WorkerReportsProgress = true; worker.DoWork += Worker_DoWork; worker.ProgressChanged += Worker_ProgressChanged; worker.RunWorkerCompleted += Worker_RunWorkerCompleted; worker.RunWorkerAsync(); } private void Worker_DoWork(object sender, DoWorkEventArgs e) { for (int i = 0; i <= 100; i++) { // Simulating long process System.Threading.Thread.Sleep(50); ((BackgroundWorker)sender).ReportProgress(i); } } private void Worker_ProgressChanged(object sender, ProgressChangedEventArgs e) { progressBar.Value = e.ProgressPercentage; lblStatus.Text = $"Progress: {e.ProgressPercentage}%"; } private void Worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { lblStatus.Text = "Operation completed!"; } ``` The issue arises when I start the task multiple times in quick succession. Occasionally, the UI updates get mixed up, and the progress bar jumps to an incorrect value, or the label does not update at all. I'm running this on .NET Framework 4.8 and using Visual Studio 2019. I've confirmed that the `bgWorker.WorkerReportsProgress` is set to true. I've tried adding a lock around the `ReportProgress` method call, but it hasn't resolved the issue. Here's that attempt: ```csharp private void Worker_DoWork(object sender, DoWorkEventArgs e) { for (int i = 0; i <= 100; i++) { System.Threading.Thread.Sleep(50); lock(worker) { ((BackgroundWorker)sender).ReportProgress(i); } } } ``` This seems to not help at all, and I often get an `InvalidOperationException` indicating that the operation is being performed on an invalid thread. Any insights on what might be causing this issue or how I can ensure the UI updates correctly? I would appreciate any tips on best practices when using `BackgroundWorker` in WinForms. I'm working with Csharp in a Docker container on Ubuntu 22.04.