IValueConverter not working for SolidColorBrush

Question

I have a progress bar that I want to change color depending on a boolean value; true is green and false is red. I have code that seems like it should work (it returns the correct value when I bind it to a textbox) but not when it's the color property of the progress bar. The converter is defined as this (in App.xaml.cs since I want to access it anywhere):

public class ProgressBarConverter : System.Windows.Data.IValueConverter
{
    public object Convert(
        object o, 
        Type type, 
        object parameter, 
        System.Globalization.CultureInfo culture)
    {
        if (o == null)
            return null;
        else
            //return (bool)o ? new SolidColorBrush(Colors.Red) : 
            //                 new SolidColorBrush(Colors.Green);
            return (bool)o ? Colors.Red : Colors.Green;
    }

    public object ConvertBack(
        object o, 
        Type type, 
        object parameter, 
        System.Globalization.CultureInfo culture)
    {
        return null;
    }
}

I then add the following to the App.xaml (so it can be a global resource):

<Application.Resources>
    <local:ProgressBarConverter x:Key="progressBarConverter" />
    <DataTemplate x:Key="ItemTemplate">
        <StackPanel>
            <TextBlock Text="{Binding name}" Width="280" />
            <TextBlock Text="{Binding isNeeded, 
                          Converter={StaticResource progressBarConverter}}" />
            <ProgressBar>
                <ProgressBar.Foreground>
                    <SolidColorBrush Color="{Binding isNeeded, 
                             Converter={StaticResource progressBarConverter}}" />
                </ProgressBar.Foreground>
                <ProgressBar.Background>
                    <SolidColorBrush Color="{StaticResource PhoneBorderColor}"/>
                </ProgressBar.Background>
            </ProgressBar>
        </StackPanel>
    </DataTemplate>
</Application.Resources>

I added the following to MainPage.xaml to display them:

<Grid x:Name="LayoutRoot" Background="Transparent">
    <ListBox x:Name="listBox" 
             ItemTemplate="{StaticResource ItemTemplate}"/>
</Grid>

And then in MainPage.xaml.cs, I define a class to hold the data and bind it to the listBox:

namespace PhoneApp1
{
    public class TestClass
    {
        public bool isNeeded { get; set; }
        public string name { get; set; }
    }

    public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        public MainPage()
        {
            InitializeComponent();

            var list = new LinkedList<TestClass>();
            list.AddFirst(
                                new TestClass { 
                                    isNeeded = true, name = "should be green" });
            list.AddFirst(
                                new TestClass { 
                                    isNeeded = false, name = "should be red" });
            listBox.ItemsSource = list;
        }
    }
}

I've attached a minimal working example so it can just be built and tested. An image of the output is here:

It returns the values from the converter for the textbox but not the progress bar. When I run the debugger, it doesn't even call it.

Thanks for any help!

Answer 1

Try to modify your converter to return a SolidColorBrush and then bind directly to your ProgressBars Foreground property.