Deleting a window's background image WPF - wpf

Question

I'm having a problem in WPF where a window doesn't release it's file-lock on the background image file after closing, before another part of the application tries to write to the image.
So as an example; say I have a WPF app consisting of 3 windows, 1 "menu" selection window and 2 others. Both of the windows create an ImageBrush using a BitmapImage as the ImageSource (the same image).
Window A has a button that when pressed, cycles through the available background images by copying them each over the file used as the original ImageSource and creating a new ImageBrush and setting the Window.Background to the new brush.
Window B simply uses the ImageBrush to draw the Window.Background.
If Window A is launched, backgrounds switched, closed and then Window B launched, everything is fine.
If Window B is launched, closed, then Window A is launched and backgrounds switched it crashes. Trying to switch the backgrounds throws an IOException because:
"The process cannot access the file 'C:\Backgrounds\Background.png' because it is being used by another process."
So Window B must still be holding onto it somehow!? I have tried doing a GC.Collect(); GC.WaitForPendingFinalizers(); to see if that cures the problem but it doesn't.

Answer 1

The answer Thomas gave is correct, and works well if you have a file path, don't want to cache the bitmap, and don't want to use XAML.
However it should also be mentioned that BitmapImage has a built-in way to load the bitmap immediately by setting BitmapCacheOption:
BitmapImage img = new BitmapImage { CacheOption = BitmapCacheOption.OnLoad };
img.BeginInit();
img.UriSource = imageUrl;
img.EndInit();
or
<BitmapImage CacheOption="OnLoad" UriSource="..." />
This will load the bitmap immediately and explicitly close the stream, just as using a FileStream would, but with several differences:
It will work with any Uri, such as a pack:// Uri.
It can be used directly from XAML
The bitmap is cached in the bitmap cache, so future use of the same Uri won't go to the disk. In your particular application this may be a bad thing, but for other uses it may be a desirable feature.

Answer 2

I assume you're loading the image directly from the file, like that ?
BitmapImage img = new BitmapImage();
img.BeginInit();
img.UriSource = imageUrl;
img.EndInit();
Try to load it from a stream instead ; that way you can close the stream yourself after the image is loaded, so that the file isn't locked :
BitmapImage img = new BitmapImage();
using (FileStream fs = File.OpenRead(imageFilePath)
{
img.BeginInit();
img.StreamSource = fs;
img.EndInit();
}