WPF application, freeing resources (images).

Question

Hi, i have a slideshow application showing some images. I have a simple usercontrol that displays an image. I read the images from an XMl file and each time i create a new instance on a new usercontrol and show it in my application. At some point i need to "refresh" theimages (e.g. new version) i remove all my usercontrols from the application and "null" them - then i try to delete all images on disc. However, this gives me an exception that the resource "myimage.png" is in use by another process and cannot be deleted. What do i have to do to "release" my resources so that i can delete them?

cheers,

Answer 1

I had a similar problem - I needed to provide an image preview using a temporary file for the image. Once the preview was closed I wanted to delete the file.

I used an explicit stream instead of a URI to load the image:

BitmapImage imageSource = new BitmapImage();

FileStream imageStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read | FileShare.Delete);

imageSource.BeginInit();

imageSource.StreamSource = imageStream;

imageSource.EndInit();

// imagePreview is a WPF Image
imagePreview.Source = imageSource;

Then when it was time to close the UI and release the image I explicitly closed the stream:

BitmapImage imageSource = imagePreview.Source as BitmapImage;
imagePreview.Source = null;

if (null != imageSource)
{
    System.IO.Stream stream = imageSource.StreamSource;

    imageSource.StreamSource = null;

    if (null != stream)
    {
        stream.Close();
    }

    // now the file can be deleted
    File.Delete(filePath);
}

Answer 2

I've looked at the WPF source code using .NET Refector and found this answer to a related question that might be a better solution for you. Set the BitmapImage.CacheOption to BitmapCacheOption.OnLoad forces the image data into memory and closes the file immediately.

Using that option, you can delete the from the file system at any time afterwards.