WPF Converter and NotifyOnTargetUpdated exclusive in a binding ?
- by Mathieu Garstecki
Hi,
I have a problem with a databinding in WPF.
When I try to use a value converter and set the NotifyOnTargetUpdated=True property to True, I get an XamlParseException with the following message:
'System.Windows.Data.BindingExpression'
value cannot be assigned to property
'Contenu' of object
'View.UserControls.ShadowedText'.
Value cannot be null. Parameter name:
textToFormat Error at object
'System.Windows.Data.Binding' in
markup file
'View.UserControls;component/saletotal.xaml'
Line 363 Position 95.
The binding is pretty standard:
<my:ShadowedText Contenu="{Binding Path=Total,
Converter={StaticResource CurrencyToStringConverter},
NotifyOnTargetUpdated=True}"
TargetUpdated="MontantTotal_TargetUpdated">
</my:ShadowedText>
(Styling properties removed for conciseness)
The converter exists in the resources and works correctly when NotifyOnTargetUpdated=True is removed. Similarly, the TargetUpdated event is called and implemented correctly, and works when the converter is removed.
Note: This binding is defined in a ControlTemplate, though I don't think that is relevant to the problem.
Can anybody explain me what is happening ? Am I defining the binding wrong ? Are those features mutually exclusive (and in this case, can you explain why it is so) ?
Thanks in advance.
More info: Here is the content of the TargetUpdated handler:
private void MontantTotal_TargetUpdated(object sender, DataTransferEventArgs e)
{
ShadowedText textBlock = (ShadowedText)e.TargetObject;
double textSize = textBlock.Taille;
double delta = 5;
double defaultTaille = 56;
double maxWidth = textBlock.MaxWidth;
while (true)
{
FormattedText newFormat = new FormattedText(textBlock.Contenu,
CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
new Typeface("Calibri"), textSize,
(SolidColorBrush) Resources["RougeVif"]);
if (newFormat.Width < textBlock.MaxWidth && textSize <= defaultTaille)
{
if ((Math.Round(newFormat.Width) + delta) >= maxWidth || textSize == defaultTaille)
{
break;
}
textSize++;
}
else
{
if ((Math.Round(newFormat.Width) - delta) <= maxWidth && textSize <= defaultTaille)
{
break;
}
textSize--;
}
}
textBlock.Taille = textSize;
}
The role of the handler is to resize the control based on the length of the content. It is quite ugly but I want to have the functional part working before refactoring.
