[c#] Change WPF window background image in C# code

I have a couple of Images configured as application resources.

When my application starts, the background of the main window is set via XAML:

<Window.Background>
    <ImageBrush ImageSource="/myapp;component/Images/icon.png" />
</Window.Background>

If a given event occurs, I'd like to change this background to another resource ("/myapp;component/Images/icon_gray.png").

I've tried using two constants:

private static readonly ImageBrush ENABLED_BACKGROUND =
    new ImageBrush(new BitmapImage(new Uri("/myapp;component/Images/icon.png")));
private static readonly ImageBrush DISABLED_BACKGROUND =
    new ImageBrush(new BitmapImage(new Uri("/myapp;component/Images/icon_gray.png")));

... but naturally, I get an exception with Invalid URI.

Is there a simple way to change the background image (via this.Background = ...) of a WPF window using either the pack Uri or the resource (i.e.: Myapp.Properties.Resources.icon)?

Here the XAML Version

<Window.Background>
    <ImageBrush>
        <ImageBrush.ImageSource>
            <BitmapImage UriSource="//your source .."/>
        </ImageBrush.ImageSource>
    </ImageBrush>
</Window.Background>

i just place one image in " d drive-->Data-->IMG". The image name is x.jpg:

And on c# code type

ImageBrush myBrush = new ImageBrush();

myBrush.ImageSource = new BitmapImage(new Uri(BaseUriHelper.GetBaseUri(this), "D:\\Data\\IMG\\x.jpg"));

(please put double slash in between path)

this.Background = myBrush;

finally i got the background..

The problem is the way you are using it in code. Just try the below code

public partial class MainView : Window
{
    public MainView()
    {
        InitializeComponent();

        ImageBrush myBrush = new ImageBrush();
        myBrush.ImageSource =
            new BitmapImage(new Uri("pack://application:,,,/icon.jpg", UriKind.Absolute));
        this.Background = myBrush;
    }
}

You can find more details regarding this in
http://msdn.microsoft.com/en-us/library/aa970069.aspx

I have been trying all the answers here with no success. Here is the simplest way to do it with ms-appx

        ImageBrush myBrush = new ImageBrush();
        Image image = new Image();
        image.Source = new BitmapImage(new Uri(@"ms-appx:///Assets/background.jpg"));
        myBrush.ImageSource = image.Source;
        TheGrid.Background = myBrush;

Assets folder is in the first level of my project, so make sure to change the path as convenient.

Uri resourceUri = new Uri(@"/cCleaner;component/Images/cleanerblack.png", UriKind.Relative);
            StreamResourceInfo streamInfo = Application.GetResourceStream(resourceUri);
            BitmapFrame temp = BitmapFrame.Create(streamInfo.Stream);
            var brush = new ImageBrush();
            brush.ImageSource = temp;
            frame8.Background = brush;

img.UriSource = new Uri("pack://application:,,,/images/" + fileName, UriKind.Absolute);