WPF Image element locks my local file

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When using the Image element and specifying a local resource Uri in the Source attribute that resource will be locked by your application's process.

<Image Source="C:\Image\Josh.png" />

The file can't be deleted or modified whilst it's locked and this can be a problem if the image was generated and the application wants to clean it up when the user has finished looking at it. There is a simple work around for this, specifying the BitmapImage directly and specifying the CacheOption as OnLoad:

<Image>
    <Image.Source>
        <BitmapImage UriSource="C:\Image\Josh.png" CacheOption="OnLoad" />
    </Image.Source>
</Image>

But

However, there is one big problem with this. The UriSource doesn't work with a binding, e.g.:

<Image>
    <Image.Source>
        <BitmapImage UriSource="{Binding MyImageUrl}" CacheOption="OnLoad" />
    </Image.Source>
</Image>

The good news is, there's another workaround for this by implementing an IValueConverter that returns a BitmapImage with the CacheOption set to OnLoad.

public class UriToCachedImageConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null)
            return null;

        if (!string.IsNullOrEmpty(value.ToString()))
        {
            BitmapImage bi = new BitmapImage();
            bi.BeginInit();
            bi.UriSource = new Uri(value.ToString());
            bi.CacheOption = BitmapCacheOption.OnLoad;
            bi.EndInit();
            return bi;
        }

        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException("Two way conversion is not supported.");
    }
}

Now we can go back to using the Image tag alone, and use our new converter to return a cached BitmapImage:

<Image Source="{Binding MyImageUrl, Converter={StaticResource uriToImageConv}}"/>

... where uriToImageConv is the key of a static resource of type UriToCachedImageConverter.

Thanks to WiredPrairie for the inspiration for this workaround.

Tags: WPF

Post By Josh Twist

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12:58
07 Aug 2007

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Comments:

Posted by GioGio @ 19 Nov 2008 02:41
hey there,
that's exactly, what I needed. Thx for that.
Now, I have a question:
I added the Class UriToCachedImageConverter to my project, but how can I add a "static resource" of this class?

Posted by Josh @ 19 Nov 2008 12:05
Check out this post, Xaml. Using Resources:

http://www.thejoyofcode.com/Xaml._Using_Resources.aspx

Posted by Ryan O'Neill @ 04 Feb 2009 02:41
Brilliant, I kind of thought it was doing something like that but I just could not track it down. Now I can delete my images after I remove them from a ListView.

Thanks for post, it was very helpful.
Ryan

Posted by Patrik Fatoric @ 10 Feb 2009 16:06
Hi,

I have a similar problem, but my image is part of control template in a Button which is situated in a DataTemplate of WPF DataGrid.
The DataTemplate is loaded dynamically as resource dictionary.

My problem is that I cannot use local resurces statically linked to my DataTemplate so I cannot
use the DataConverter.

What could I do ?

I find out, when I intentional chage the ImageSource to another existing image on disk the system release the first one. After that the first image is free to delete or chage.

Is there a better solution ?

My code ...

<Button x:Name="Img1" Width="35" Height="35">
<Button.Template>
<ControlTemplate>
<Image x:Name="img" Source="{Binding Path=Slika}" width="32" Height="32"/></ControlTemplate> </Button.Template>

But

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