MultiBinding returns a value but the value is not set in the width property

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WPF

Binding

rectangle

Hi all

I have a piece of code sample which suppose to set the width of the rectangle from a converter. I can see the converter is called twice (the second time with the required value) but the value does not seem to reach the Width property of the rectangle.

note: I use rectangle on purpose instead of a progressbar - requirements

Here is the xaml

<Window.Resources>
    <viewmodel:CalcWidthFromPercentageConverter x:Key="CalcWidthFromPercentageConverter" />
</Window.Resources>
<Window.DataContext>
    <viewmodel:ViewModel/>
</Window.DataContext>
<Grid>
    <Border x:Name="borderParent" Height="20" HorizontalAlignment="Stretch" BorderBrush="Black" BorderThickness="1" VerticalAlignment="Center">
        <Rectangle Fill="Red" Height="20" HorizontalAlignment="Left">
            <Rectangle.Width>
                <MultiBinding Converter="{StaticResource CalcWidthFromPercentageConverter}">
                    <Binding Path="ProgressWidthPercentage"/>
                    <Binding Path="ActualWidth" ElementName="borderParent"></Binding>
                </MultiBinding>
            </Rectangle.Width>
        </Rectangle>
    </Border>
</Grid>

here is the converter

public class CalcWidthFromPercentageConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values.Count() == 2)
{
decimal inputPercentage = (decimal)values[0];
decimal borderWidth = System.Convert.ToDecimal(values[1]);
decimal result = borderWidth * inputPercentage;
return result;
}
return values;
}

public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
return new[] { value };
}
}

and last the viewmodel

public class ViewModel
{
private readonly decimal _progressWidthPercentage;

public decimal ProgressWidthPercentage
{
get { return _progressWidthPercentage; }
}

public ViewModel()
{
_progressWidthPercentage = (decimal)0.37;
}
}