Binding a Distinction basedon Actual Width to Visibility - wpf

Question

Is it possible to bind an ActualWidth or Width property of a Control to the Visibility of another Control with a distinction about value (like <200)? In my Opinion it is only possible with a converter because a DataTrigger can not work with > or <.
So I tried it with a Converter but it didn't work. I'm not sure which BindingMode is necessary and which kind of converter I need for such a solution.
The xaml code:
<StackPanel>
<Slider x:Name="slider" Height="36" Width="220" Maximum="500"/>
<Rectangle x:Name="mover" Height="12" Stroke="Black" Width="{Binding Value, ElementName=slider}"/>
<Rectangle x:Name="rectangle" Fill="#FFFF9E0E" Height="34" Width="112" Visibility="{Binding ActualWidth, Converter={StaticResource umkehr}, ElementName=rectangle, Mode=OneWay}"/>
</StackPanel>
and the idea for the converter:
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value != null) {
var val = System.Convert.ToDouble(value);
if (val > 100)
return Visibility.Visible;
return Visibility.Collapsed;
}
return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}

Answer 1

It is likely not working because you are binding your Rectangle's Visibility to the same rectangle's ActualWidth, and an invisible rectangle will always have a width of 0, so will never be visible.
Here's some examples. One binds to the other rectangle's ActualWidth, and the other binds to your Slider's Value
<Rectangle x:Name="rectangle"
Visibility="{Binding ActualWidth, ElementName=mover,
Converter={StaticResource umkehr}}"/>
or
<Rectangle x:Name="rectangle"
Visibility="{Binding Value, ElementName=slider,
Converter={StaticResource umkehr}}"/>
And as far as I know, there's no easy way of basing a value off of if something is greater than or less than a value. Coverters are your best option.

Answer 2

ActualWidth is a readonly property exposed by FrameworkElement class -
public double ActualWidth { get; }
It is get only property hence you can't set it to other value from code. You can bind to Width of your control instead to make it work.
EDIT
This works for me, may be this is what you want -
Converter
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is double)
{
return ((double)value > 100) ? Visibility.Visible : Visibility.Collapsed;
}
return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
XAML
<StackPanel>
<Slider x:Name="slider" Height="36" Width="220" Maximum="500"/>
<Rectangle x:Name="mover" Height="12" Stroke="Black" Width="{Binding Value, ElementName=slider}"/>
<Rectangle x:Name="rectangle" Fill="#FFFF9E0E" Height="34" Width="112" Visibility="{Binding ActualWidth, Converter={StaticResource MyConverter}, ElementName=mover, Mode=OneWay}"/>
</StackPanel>

Answer 3

If you're attempting to change the Visibility of a control based on the ActualWidth of another control, you'll either need to use a IValueConverter or you're own type of MarkupExtension (inherit from Binding or BindingBase).
Converter Option:
[ValueConversion(typeof(Double), typeof(Visibility))]
[ValueConversion(typeof(Double?), typeof(Visibility))]
public class MinimumLengthToVisibilityConverter : IValueConverter
{
public Double MinLength { get; set; }
public override Object Convert(Object value, Type targetType, Object parameter, CultureInfo culture)
{
if ((value == null) || !(value is Double))
{
return DependencyProperty.UnsetValue;
}
return (((Double)value) > MinLength) ? Visibility.Visible : Visibility.Collapsed;
}
public override Object ConvertBack(Object value, Type targetType, Object parameter, CultureInfo culture)
{
return DependencyProperty.UnsetValue;
}
}
MarkupExtension Option:
Read this blog post to get a better feel for how to implement this...

Answer 4

You can actually have the value in a parameter, so you can re-use the converter if you need to:
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
double cutoff = 0.0;
if(parameter is double)
{
cutoff = (double)parameter;
}
if (parameter is string)
{
Double.TryParse(parameter.ToString(), out cutoff);
}
if (value is double)
{
return ((double)value > cutoff) ? Visibility.Visible : Visibility.Collapsed;
}
return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
And the XAML:
<StackPanel>
<Slider x:Name="slider" Height="36" Width="220" Maximum="500"/>
<Rectangle x:Name="mover" Height="12" Stroke="Black" Width="{Binding Value, ElementName=slider}"/>
<Rectangle x:Name="rectangle" Fill="#FFFF9E0E" Height="34" Width="112"
Visibility="{Binding ActualWidth, Converter={StaticResource ActualWidthToVisibilityConverter},
ElementName=mover, Mode=OneWay, ConverterParameter=100}"/>
</StackPanel>