Binding Error in Style in DrawingImage

Question

<Window x:Class="Project.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="100" Height="400">

    <Window.Resources>
        <Style x:Key="IconStyle" TargetType="{x:Type Image}">
            <Setter Property="Source">
                <Setter.Value>
                    <DrawingImage>
                        <DrawingImage.Drawing>
                            <GeometryDrawing Brush="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentControl}}, Path=Foreground}">
                                <GeometryDrawing.Geometry>
                                    <PathGeometry Figures="M 0,0 0,10 10,5" />
                                </GeometryDrawing.Geometry>
                            </GeometryDrawing>
                        </DrawingImage.Drawing>
                    </DrawingImage>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

    <StackPanel>

        <ContentControl Foreground="Red">
            <Image Style="{StaticResource IconStyle}" />
        </ContentControl>

        <ContentControl Foreground="Blue">
            <Image Style="{StaticResource IconStyle}" />
        </ContentControl>

    </StackPanel>

</Window>

This example shows two icons. The icons have the color of the parent ContentControl. It works fine.

But the output shows a binding error:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.ContentControl', AncestorLevel='1''. BindingExpression:Path=Foreground; DataItem=null; target element is 'GeometryDrawing' (HashCode=8154127); target property is 'Brush' (type 'Brush')

Why does this error occur? How can I fix it or can I ignore?

EDIT

The error occurs also in this case:

<Window x:Class="Project.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="100" Height="400">

    <Window.Resources>
        <Style x:Key="IconStyle" TargetType="{x:Type ContentControl}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ContentControl">
                        <Image>
                            <Image.Source>
                                <DrawingImage>
                                    <DrawingImage.Drawing>
                                        <GeometryDrawing Brush="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentControl}}, Path=Foreground}">
                                            <GeometryDrawing.Geometry>
                                                <PathGeometry Figures="M 0,0 0,10 10,5" />
                                            </GeometryDrawing.Geometry>
                                        </GeometryDrawing>
                                    </DrawingImage.Drawing>
                                </DrawingImage>
                            </Image.Source>
                        </Image>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

    <StackPanel>    
        <ContentControl Foreground="Red" Style="{StaticResource IconStyle}" />    
        <ContentControl Foreground="Blue" Style="{StaticResource IconStyle}" />    
    </StackPanel>

</Window>

You have multiple ContentControls, this might cause a problem with your RelativeSource binding (even if it worked), have you tried using an ElementName binding instead? — Mike Eason
The error occurs also if I use ElementName binding or if I delete one of the two ContentControls. — Jotrius
It's pretty weird, I mean, it does work, but it throws an error anyway. It'd be tempting to ignore it, however there must be some reason why it's throwing an error. The truth is, I don't know. — Mike Eason
Out of curiosity, what if you pass your color string through the Tag property instead of Foreground ? Seems like a color collision. — Chris W.
The error occurs also if I use the Tag property of the ContentControl. — Jotrius

Dragos Stoica Dragos Stoica · Accepted Answer · 2015-03-19T11:51:31

Just set a name and the error will disappear:

  <GeometryDrawing x:Name="GeometryDrawing" Brush="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Foreground}">
                                        <GeometryDrawing.Geometry>
                                            <PathGeometry Figures="M 0,0 0,10 10,5" />
                                        </GeometryDrawing.Geometry>
                                    </GeometryDrawing>

A more fancy way for binding to Parent:

   RelativeSource={RelativeSource TemplatedParent}

EDIT:

If you want to supress this VS errors, visit the link

Binding Error in Style in DrawingImage

1 Answers