Foreground property binding is not working

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I have a textblock, the text's foreground's color should change by the value. However it is not working well.

<TextBlock Text="{Binding Path=Foo}" 
           Foreground="{Binding Path=Foo, Converter={StaticResource myConverter}" />

The converter part likes

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var temp = (int)value;
        if (temp <100 && temp>50)
        {
           return "#ff23d3";
        }
       if(temp>200)
           return "da2367";
       return new SolidBrush(Colors.Green);
    }

But although the values are different, it only return one color.

What I have tried:

I set the break point in the code. It did reach the right place.
Maybe type conversion is wrong?

Posted 16-Nov-17 13:27pm

Member 12658724

Updated 16-Nov-17 21:52pm

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Kenneth Haugland 16-Nov-17 20:38pm

What is it bonded to? Did you implement INotifyChanged on that property?

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Graeme_Grant · Accepted Answer · 2017-11-16T21:52:00

First things first, the Foreground[^] Dependency Property[^] of the of any WPF Control[^] is expecting a Brush[^].

Armed with this knowledge, we can now look at your Converter:

C#

public object Convert(object value,
                      Type targetType,
                      object parameter,
                      System.Globalization.CultureInfo culture)
{
    var temp = (int)value;
    if (temp <100 && temp>50)
    {
       return "#ff23d3";
    }
    if(temp>200)
       return "da2367";
    return new SolidBrush(Colors.Green);
}

1. "#ff23d3" = string hex color value (not color object), not a Brush of any kind.

2. "da2367" is a string. Not the same as the first, but still not a Brush.

3. new SolidBrush(Colors.Green) - This is a Solid Color Brush. This will work.

So, to fix, you need to convert a color value to a Color class[^] that can be used with a Brush:

C#

using System.Windows.Media;

Color color = (Color)ColorConverter.ConvertFromString("#FFFF23D3");

Now that you have a Color object you can apply it to a SolidColorBrush[^]:

C#

return new SolidBrush(color);

So, your fixed Converter will look like:

C#

public object Convert(object value,
                     Type targetType,
                     object parameter,
                     System.Globalization.CultureInfo culture)
{
    var temp = (int)value;

    if (temp <100 && temp>50)
       return new SolidColorBrush(
           (Color)ColorConverter
               .ConvertFromString("#FFFF23D3"));

    if(temp>200)
       return new SolidColorBrush(
           (Color)ColorConverter
               .ConvertFromString("#FFDA2367"));

       return new SolidColorBrush(Colors.Green);
}