Question

This code is from my C# WPF application:

public MainWindow()
{
    InitializeComponent();
    status("Getting dl links");
    getLinks();
}

The procedure getLinks currently displays a couple of links in a messagebox. Those links are displayed in a messagebox before the WPF application becomes visible.
In this is case not a problem, but how would I show progress (like a progressbar) of any
procedure I want to load at startup?

Answer 1

Here is an example on how you can do it. To simplify it a bit, I added the controls directly in the MainWindow constructor, but I would prefer to do this with XAML.

public MainWindow()
{
    InitializeComponent();

    var progressBar = new ProgressBar();
    progressBar.Height = 40;
    progressBar.Width = 200;
    progressBar.Margin = new Thickness(100, 100, 100, 100);

    Task.Factory.StartNew(() =>
    {
        // getLinks();
        for (var i = 0; i < 5; i++)
        {
            Dispatcher.Invoke(new Action(() => { progressBar.Value += 20; }));

            Thread.Sleep(500);
        }
    });

    var stackPanel = new StackPanel();
    stackPanel.Children.Add(progressBar);

    Content = stackPanel;

}

I first add a ProgressBar somewhere on the interface to make it visible for this demo and then I add it to a new StackPanel, it could be any panel at all, in this case it doesn’t matter.

To load the links on another thread, I create a new Task, this is a part of the TPL (Task Parallel Library) in .NET 4.0. In this case I am simulating that getLinks() takes 5 * 500 milliseconds to run and that it in fact is five links that will be loaded, hence 20% each iteration.

What I do then is that I add 20 to the progressBar value, which indicates that it increased with 20%.

This line might confuse you a bit

Dispatcher.Invoke(new Action(() => { progressBar.Value += 20; }));

But it is in fact quite common when you do cross-thread programming with GUI. So the problem is that you are on another thread here, we started of a Task that will run on a separate thread, and you cannot update your UI thread from another thread. So what you need is something called a Dispatcher, and this is accessable from within your Window-class.

Then you Invoke an action on it, which means that you simply say “Run this piece of code on this thread for me”.

And if you want to display a MessageBox when everything is loaded, you can simply add a MessageBox.Show("Loaded!"); after the for-loop.