matthew_b matthew_b - 3 months ago 24
C# Question

Binding fails when using SolidColorBrush resource on Stroke property

I have created a

UserControl
and have quite a few bindings to several custom DependencyProperties in the control. For some reason though, one of these is failing with the error:


System.Windows.Data Error: 4 : Cannot find source for binding with
reference 'ElementName=YearSelectorControl'.
BindingExpression:Path=SelectedBorderColor; DataItem=null; target
element is 'SolidColorBrush' (HashCode=45568629); target property is
'Color' (type 'Color')


The control includes a
ToggleButton
and
Popup
. The error occurs when the
Popup
is opened by clicking on the
ToggleButton
.

Here is the xaml:

<UserControl x:Class="MyProject.Views.YearSelector"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:MyProject.Views"
mc:Ignorable="d"
d:DesignHeight="23" d:DesignWidth="181"
x:Name="YearSelectorControl">
<UserControl.Resources>
<SolidColorBrush x:Key="HoverColorBrush" Color="{Binding ElementName=YearSelectorControl, Path=HoverColor}"/> <!--This binding is virtually identical, but works fine-->
<SolidColorBrush x:Key="SelectedBorderColorBrush" Color="{Binding ElementName=YearSelectorControl, Path=SelectedBorderColor}"/> <!--This is the binding that fails-->
<local:YearToBackColorConverter x:Key="YearToBackColorConverter"/>
<local:YearToBorderThicknessConverter x:Key="YearToBorderThicknessConverter"/>

<Style x:Key="ForwardBackButtons" TargetType="{x:Type Button}" >
<Setter Property="Background" Value="Transparent" />
<Setter Property="BorderThickness" Value="0" />
<Setter Property="FontFamily" Value="Arial" />
</Style>
<ControlTemplate x:Key="YearButton" TargetType="{x:Type Button}">
<Grid Width="55" Height="30" Margin="2">
<Rectangle x:Name="ButtonRectangle" Stroke="{StaticResource SelectedBorderColorBrush}"> <!--Use of the failing brush-->
<!--Removed code that determines StrokeThickness. Works correctly if Stroke set to a specific color rather than a Static Resource-->
</Rectangle>
<ContentPresenter VerticalAlignment="Center" HorizontalAlignment="Center"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="ButtonRectangle" Property="Fill" Value="{StaticResource HoverColorBrush}"/> <!--Use of the properly binding brush-->
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</UserControl.Resources>

<Grid>
<!--Layout here-->
</Grid>
</UserControl>


Here is an excerpt from the code-behind for the two
DependencyProperties
that are bound to
SolidColorBrush
resources:

public Color HoverColor
{
get { return (Color)GetValue(HoverColorProperty); }
set { SetValue(HoverColorProperty, value); }
}
public static readonly DependencyProperty HoverColorProperty =
DependencyProperty.Register("HoverColor", typeof(Color), typeof(YearSelector), new PropertyMetadata(Color.FromArgb(255,190,230,253)));

public Color SelectedBorderColor
{
get { return (Color)GetValue(SelectedBorderColorProperty); }
set { SetValue(SelectedBorderColorProperty, value); }
}
public static readonly DependencyProperty SelectedBorderColorProperty =
DependencyProperty.Register("SelectedBorderColor", typeof(Color), typeof(YearSelector), new PropertyMetadata(Color.FromArgb(255,126,0,234)));

Answer

I went away from this for a few months to focus on more important elements of my application and have finally come back to it. I discovered the solution, though I'm not sure why it was a problem in the first place.

For whatever reason, binding a SolidColorBrush resource to the Stroke property doesn't work. What I did instead, is I bound the Color DependencyProperty directly to Stroke and used an IValueConverter to convert it to a SolidColorBrush.

XAML:

<Rectangle x:Name="ButtonRectangle" Stroke="{Binding ElementName=YearSelectorControl, Path=SelectedBorderColor, Converter={StaticResource ColorToSolidColorBrushConverter}}">

Code-behind:

public class ColorToSolidColorBrushConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        try
        {
            Color c = (Color)value;
            return new SolidColorBrush(c);
        }
        catch
        {
            return new SolidColorBrush(Color.FromRgb(0,0,0));
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}