How do I load images in the background?

Question

I am trying to load an image in the background and then update the UI. I have been playing with this all day and I don\'t know what I am missing. I keep getting the follow

Answer 1

What I tend to use the ThreadPool.QueueUserWorkItem to load the image, then when the operation completes I call back to the UI thread using the thread-safe Dispatcher object. The image source is not thread safe, you will have to use something like the JpegBitmapDecoder, there is also a PngBitmapDecoder.

For Example:

public Window()
{
    InitializeComponent();

    ThreadPool.QueueUserWorkItem(LoadImage,
         "http://z.about.com/d/animatedtv/1/0/1/m/simp2006_HomerArmsCrossed_f.jpg");
}

public void LoadImage(object uri)
{
    var decoder = new JpegBitmapDecoder(new Uri(uri.ToString()), BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad);
    decoder.Frames[0].Freeze();
    this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(SetImage), decoder.Frames[0]);
}

public void SetImage(ImageSource source)
{
    this.BackgroundImage.Source = source;
}