CODEWITHSUNDEEP
c#wpfxamlbindingdependency-properties
user1145533
user1145533

Reputation: 697

Binding DependencyProperty to a usercontrol

I have created a dependency property but for some reason it seems to be failing, it must be sothing to do with the binding but I can't see what. The dependency property is as follows:

public class HighlightColour
{
    #region HighlightColour dependency property

    public static readonly DependencyProperty sm_ValueProperty;

    public static Color GetValue(DependencyObject obj)
    {
        return (Color)obj.GetValue(sm_ValueProperty);
    }

    public static void SetValue(DependencyObject obj, Color value)
    {
        obj.SetValue(sm_ValueProperty, value);
    }

    #endregion

    static HighlightColour()
    {
        var metadata = new FrameworkPropertyMetadata(Colors.Transparent);
        sm_ValueProperty = DependencyProperty.RegisterAttached("Value",
                                                   typeof(Color),
                                                   typeof(HighlightColour), metadata);
    }
}

In the XAML I am trying to bind to this in a style template and set the background colour of a button:

<Style x:Key="CommonButton" TargetType="Button">
    <Setter Property="FontFamily" Value="Tahoma"/>
    <Setter Property="FontSize" Value="12"/>
    <Setter Property="custprop:HighlightColour.Value" Value="Red"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type Button}">
                <Grid Margin="0">
                    <Border Name="ButtonBody" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="1" CornerRadius="12,12,12,12" />
                    <Border Name="Highlight" Opacity="0" BorderThickness="0" CornerRadius="12,12,12,12">
                        <Border.Background>
                            <SolidColorBrush Color="{Binding Path=(custprop:HighlightColour.Value), Source={RelativeSource FindAncestor,AncestorType={x:Type Button}}}"/>
                        </Border.Background>
                    </Border>
                    <ContentPresenter Name="content" HorizontalAlignment="Center" VerticalAlignment="Center" />
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsMouseOver" Value="True">
                        <Trigger.EnterActions>
                            <BeginStoryboard Name="HighlightAnim">
                                <Storyboard TargetName="Highlight" TargetProperty="Opacity" AutoReverse="True" RepeatBehavior="Forever">
                                    <DoubleAnimation From="1" To="0.2" Duration="00:00:01"/>
                                </Storyboard>
                            </BeginStoryboard>
                        </Trigger.EnterActions>
                        <Trigger.ExitActions>
                            <StopStoryboard BeginStoryboardName="HighlightAnim"/>
                        </Trigger.ExitActions>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

For some reason it is failing and I see errors such as:

Cannot get 'Value' value (type 'Color') from '' (type 'RelativeSource'). BindingExpression:Path=(0); DataItem='RelativeSource' (HashCode=60828848); target element is 'SolidColorBrush' (HashCode=10588721); target property is 'Color' (type 'Color') InvalidCastException:'System.InvalidCastException: Unable to cast object of type 'System.Windows.Data.RelativeSource' to type 'System.Windows.DependencyObject'.

Upvotes: 1

Views: 4063

Answers (2)

Louis Kottmann
Louis Kottmann

Reputation: 16618

Change:

    <SolidColorBrush Color="{Binding Path=(custprop:HighlightColour.Value), 
                     Source={RelativeSource FindAncestor,AncestorType={x:Type Button}}}" />

To:

<SolidColorBrush Color="{Binding Path=(custprop:HighlightColour.Value), 
                 RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type Button}}}" />

For more information on Binding: MSDN or this cheat sheet

Upvotes: 2

Kent Boogaart
Kent Boogaart

Reputation: 178630

Don't prefix with sm_ or WPF won't be able to "find" your DP.

Upvotes: 0

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