MultiBind on Textblock Text field fails in UWP

Noticed that a multibind will fail consistently for me when bound in UWP to the Text field of a TextBlock, noting: Unhandled exception at 0x7757DF95 (combase.dll).

Sample code:

                <TextBlock Foreground="AntiqueWhite" FontSize="12" FontWeight="Bold" Text="13.41">
                        <Interactivity:Interaction.Behaviors>
                            <cimba:MultiBindingBehavior Converter="{StaticResource IntToValConverter}" 
                                                        PropertyName="Text"  >
                                <cimba:MultiBindingItem Value="{Binding StepValue}"/>
                            </cimba:MultiBindingBehavior>
                        </Interactivity:Interaction.Behaviors>
                </TextBlock>

And the Converter:

    public class IntToValConverter : MultiValueConverterBase
    {
        public override object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (null == values[0]) return "haha";
            return "hoho";
        }
        public override object[] ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }

[pedrolamas]

Given it only happens on Release mode, we can safely assume this is due to .NET Native optimizations… I’m not sure I’ll be able to fix this on my side, but I think I have a solution for this specific case!

Add this to your app Default.rd.xml file, rebuild and try again:

<Type Name="Windows.UI.Xaml.Controls.TextBlock">
  <Property Name="Text" Serialize="Required"/>
</Type>

[pedrolamas]

Yep, I don’t think I’ll be able to do “magic” stuff over this one, but I’m hoping Microsoft might! 😉

In the meantime, here’s something to read on the subject if you want to!