Why is my ImageSource Binding not updated? - wpf

Question

I'm trying to dynamically bind an Image Source in XAML to an URI in ViewModel (MVVM). This works fine for the initial URI, the picture "C:\tmp\Test.png" is shown. But if I set another URI to ImageURI in ViewModel the picture is not updated. Can anyone help me?
XAML:
<Image x:Name="UserImage" Stretch="Fill" Grid.Row="0">
<Image.Source>
<BitmapImage CreateOptions="IgnoreImageCache" UriSource="{Binding ImageURI, UpdateSourceTrigger=Explicit, Mode=TwoWay}"/>
</Image.Source>
</Image>
ViewModel:
public string imageURI = "C:\\tmp\\Test.png";
public string ImageURI
{
get
{
return imageURI;
}
set
{
imageURI = value;
this.OnPropertyChanged("ImageURI");
}
}

Answer 1

BitmapImage implements ISupportInitialize. This means that property changes are ignored after initialization. Changing the Binding's source property has no effect.
You should directly bind the Image's Source property. Built-in automatic type conversion will create a BitmapFrame behind the scenes.
<Image Source="{Binding ImageURI}" .../>
Setting UpdateSourceTrigger=Explicit and Mode=TwoWay on the Binding is pointless.
If you need to explicitly create a BitmapImage (e.g. one where the IgnoreImageCache option is set), write an appropriate Binding Converter.

Answer 2

Pretty old question here with no solution. Sooo since i had a similar problem and used a slightly different approach, here is my solution:
Use a converter which returns a BitmapImage in this way:
public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
BitmapImage error = new();
error.BeginInit();
// OnLoad will give you errors just with the start of your application and
// and won't hide somewhere in your log
error.CacheOption = BitmapCacheOption.OnLoad;
error.UriSource = new Uri(#"pack://application:,,,/Images/error.png");
error.EndInit();
error.Freeze();
return error;
}
The binding:
<Image Source="{Binding Status, Converter={StaticResource enumAnalyzerStatusConverter}, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
The OnLoad option will give an error on startup if something is bad with your image like the path. Remember to set the image in your project explorer to Ressource.