Data Trigger using Converter not working

Question

I am trying to update the color of textblock depending on it value. Seems simple however not working.

Here's the textblock xaml.

 <TextBlock 
        Grid.Column="1" 
        Grid.Row="1" 
        Text="{Binding Path=GL, StringFormat={}{0:N0}}" 
        HorizontalAlignment="Left" 
        FontFamily="Verdana" 
        Foreground="Tomato" 
        FontWeight="Bold"             
        VerticalAlignment="Center"
        Margin="5,2,5,0"
        FontSize="18"
        >
        <TextBlock.Resources>
            <converters:ColorConverter x:Key="CoConverter"></converters:ColorConverter>
        </TextBlock.Resources>
      <TextBlock.Style>
          <Style>
              <Style.Triggers>
                  <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Text, Converter={StaticResource ResourceKey=CoConverter}}" Value="true">
                  <Setter Property="TextBlock.Foreground" Value="LimeGreen" />
                      </DataTrigger>
              </Style.Triggers>
          </Style>
      </TextBlock.Style>

Here the converter

public class ColorConverter : MarkupExtension, IValueConverter
{

    #region IValueConverter Members

    public object Convert(object value, 
        Type targetType, 
        object parameter, 
        System.Globalization.CultureInfo culture)
    {
        if (value == null)
            return false;
        if (value.ToString().Length == 0)
            return false;
        if (System.Convert.ToDouble(value) >= 0)
            return true;

        return false;
    }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }
}

The converter looks good, however the trigger is not applying for some reason.

Venule

What have you tried? have you set a breakpoint and saw that you reach the converter from the XAML? – Annexation

Yes, the Converter fires – Venule

What's the text of your textblock and what value is retuned by your converter? – Unknot

text is double number and that is same that is recd. by the converter. The converter returns true or false depending on the value greater than 0 or not. While debugging the converter looks good. – Venule

Answer 1

<TextBlock 
        Grid.Column="1" 
        Grid.Row="1" 
        Text="{Binding Path=GL, StringFormat={}{0:N0}}" 
        HorizontalAlignment="Left" 
        FontFamily="Verdana"
        FontWeight="Bold"             
        VerticalAlignment="Center"
        Margin="5,2,5,0"
        FontSize="18"
        >
        <TextBlock.Resources>
            <converters:ColorConverter x:Key="CoConverter"></converters:ColorConverter>
        </TextBlock.Resources>
      <TextBlock.Style>
          <Style>
              <Setter Property="TextBlock.Foreground" Value="Tomato" />
              <Style.Triggers>
                  <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Text, Converter={StaticResource ResourceKey=CoConverter}}" Value="true">
                  <Setter Property="TextBlock.Foreground" Value="LimeGreen" />
                      </DataTrigger>
              </Style.Triggers>
          </Style>
      </TextBlock.Style>

You need to set the Foreground property in your style to change it dynamically at runtime.

Unknot

Is your Text value will always be a double value? If not the converter code might break at this line - if (System.Convert.ToDouble(value) >= 0) return true; – Unknot

No, I have checks before that. if (value == null) return false; if (value.ToString().Length == 0) return false; – Venule

But if text will be string say "Test" in that case it will bypass your two conditions and it won't be converted to double value!! – Unknot

Highly unlikely, the text is bound to type double. There are no First chance Exceptions or anything weird in the output window. – Venule

Can i see your textblock where you apply this style? Because for me its running fine as i posted. – Unknot

Updated the Question with entire textblock – Venule

Please see my answer, it should work now. You need to set the Foreground property in your Style setter. – Unknot

Answer 2

Looks like you're missing StaticResource inside your curly braces when specifying the converter:

Converter={StaticResource converters:ColorConverter}

Karlsruhe

Still Does not work, even If define the converter as a static resource and set the converter as its resource key. – Venule

Answer 3

If you are trying to change property value dynamically, then corresponding property must be kept only in Setter tag.

<TextBlock>
  <TextBlock.Style>
      <Style>
          <Setter Property="TextBlock.Foreground" Value="Tomato" />
          <Style.Triggers>
              <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Text, Converter={StaticResource ResourceKey=CoConverter}}" Value="true">
              <Setter Property="TextBlock.Foreground" Value="LimeGreen" />
                  </DataTrigger>
          </Style.Triggers>
      </Style>
</TextBlock.Style>

But not in both TextBlock and Setter tag. To be precise for your example remove Foreground property inside the TextBlock tag as given in my code.

Uther