Bind to converter in XAML

[_Madmatt]

Hey all, I'm running into a problem when binding a property of a GroupItemTemplate (in the WP7 LongListSelector) to a converter I built. I want the converter to check if there are items to be displayed in the group, and according to if there are items, set a Brush to the background. This is my code for the Converter:

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value is Group<TrackInfo>)
{
Group<TrackInfo> group = value as Group<TrackInfo>;
if (group != null)
{
if (group.Items.Count == 0)
return (SolidColorBrush)Application.Current.Resources["PhoneChromeBrush"];
else
return (SolidColorBrush)Application.Current.Resources["PhoneAccentBrush"];
}
}

        return new SolidColorBrush(Color.FromArgb(128, 255, 0, 0));
    }

And this is in my XAML:

[Mark Salsbery]

You need to have the converter instance in resources somewhere visible to the datatemplate (just like the other static resources you are binding to) so the StaticResource binding works.

Mark Salsbery Microsoft MVP - Visual C++ :java:

modified on Wednesday, July 13, 2011 5:58 PM

[Abhinav S]

Try by making this line - ; part of the Itemsources or UserControls resource.

[_Madmatt]

The DataTemplate as well as the Converter are in the

<DataTemplate x:Key="groupItemTemplate">
        <Border Width="99" Height="99" Background="{Binding Converter={StaticResource groupItemBackgroundBrush}}" Margin="6" IsHitTestVisible="{Binding HasItems}">
            <TextBlock Text="{Binding GroupTitle}" 
                                   FontFamily="{StaticResource PhoneFontFamilySemiBold}"
                                   FontSize="36"
                                   Margin="{StaticResource PhoneTouchTargetOverhang}"
                                   Foreground="{StaticResource PhoneForegroundBrush}"                                        
                                   VerticalAlignment="Bottom"/>
        </Border>
    </DataTemplate>
    
    <valueConverters:TrackGroupToGroupItemBackgroundBrushConverter x:Key="groupItemBackgroundBrush" />
</phone:PhoneApplicationPage.Resources>

Is there something wrong in here?

[_Madmatt]

They are both part of the <phone:PhoneApplicationPage.Resources>, I cannot create a <DataTemplate.Resources>, so where should I put it else? This is quite confusing to me, it's the first time is use XAML binding in such a complex way... Thanks

[Pete OHanlon]

_Madmatt wrote:

Background="{Binding Converter={StaticResource groupItemBackgroundBrush}}"

The problem here is that you haven't told the converter what it should bind to. Try changing this to be

"{Binding Path=., Converter={StaticResource groupItemBackgroundBrush}}"

Forgive your enemies - it messes with their heads

My blog | My articles | MoXAML PowerToys | Mole 2010 - debugging made easier - my favourite utility

[_Madmatt]

No, still getting the exception with this setting... :(

[Pete OHanlon]

Put a breakpoint in your converter and see if it gets hit. Then step over the code to see what breaks.

Forgive your enemies - it messes with their heads

My blog | My articles | MoXAML PowerToys | Mole 2010 - debugging made easier - my favourite utility

[_Madmatt]

It's not even hitting the converter! :( Not with this XAML:

phone:PhoneApplicationPage.Resources
<DataTemplate x:Key="groupItemTemplate">
<Border Width="99" Height="99" Background="{Binding Path=., Converter={StaticResource groupItemBackgroundBrush}}" Margin="6" IsHitTestVisible="{Binding HasItems}">
<TextBlock Text="{Binding GroupTitle}"
FontFamily="{StaticResource PhoneFontFamilySemiBold}"
FontSize="36"
Margin="{StaticResource PhoneTouchTargetOverhang}"
Foreground="{StaticResource PhoneForegroundBrush}"
VerticalAlignment="Bottom"/>
<Border.Resources>
<valueConverters:TrackGroupToGroupItemBackgroundBrushConverter x:Key="groupItemBackgroundBrush" />
</Border.Resources>
</Border>
</DataTemplate>

</phone:PhoneApplicationPage.Resources>

And not with this one too:

phone:PhoneApplicationPage.Resources
<DataTemplate x:Key="groupItemTemplate"
<Border Width="99" Height="99" Background="{Binding Path=., Converter={StaticResource groupItemBackgroundBrush}}" Margin="6" IsHitTestVisible="{Binding HasItems}">
<TextBlock Text="{Binding GroupTitle}"
FontFamily="{StaticResource PhoneFontFamilySemiBold}"
FontSize="36"
Margin="{StaticResource PhoneTouchTargetOverhang}"
Foreground="{StaticResource PhoneForegroundBrush}"
VerticalAlignment="Bottom"/>
</Border>
</DataTemplate>

<valueConverters:TrackGroupToGroupItemBackgroundBrushConverter x:Key="groupItemBackgroundBrush" />

</phone:PhoneApplicationPage.Resources>

[skv_lviv]

Not sure, maybe I'm wrong, but have you tried to put converter definition before your datatemplate?

[_Madmatt]

Thanks! This did the trick! Too bad I didn't think of that myself... :D