C#, WPF, Updating the gui without backgroundworkers

Question

I have a program that takes 10-20 seconds to start. I need to show a window with a progress bar when the program starts up. I know BackgroundWorker\'s are the correct way to do

Answer 1

You're still doing the long task in the main thread. You need to show the loading window in the main thread and do the long task in the background.

Using a BackgroundWorker is really the simplest solution for this:

BackgroundWorker bw;
LoadingWindow lw;

public Window1() {
    bw = new BackgroundWorker();
    lw = new LoadingWindow();

    bw.DoWork += (sender, args) => {
        // do your lengthy stuff here -- this will happen in a separate thread
        ...
    }

    bw.RunWorkerCompleted += (sender, args) => {
        if (args.Error != null)  // if an exception occurred during DoWork,
            MessageBox.Show(args.Error.ToString());  // do your error handling here

        // close your loading window here
        ...
    }

    // open and show your loading window here
    ...

    bw.RunWorkerAsync(); // starts the background worker
}