Access user control property in App.xaml style WPF

Question

I'm trying to set the "Stroke" property of Path in my visual brush (Defined in App.xaml) via the property from my model. I'm using this style in my another control template in a usercontrol.

Style in User control resources:

<Ellipse x:Name="slideThumb" Height="25" Width="25" Stroke="{Binding ThumbColor, UpdateSourceTrigger=PropertyChanged}">
                        <Ellipse.Style>
                            <Style TargetType="{x:Type Ellipse}">
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding IsHatchBrush}" Value="true">
                                        <Setter Property="Fill" Value="{StaticResource HatchBrushVertical}" />
                                    </DataTrigger>
                                    <DataTrigger Binding="{Binding IsHatchBrush}" Value="false">
                                        <Setter Property="Fill" Value="{Binding ThumbColor, UpdateSourceTrigger=PropertyChanged}" />
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                        </Ellipse.Style>
                    </Ellipse>

Brush Defined in App.xaml:

<VisualBrush x:Key="HatchBrushVertical" TileMode="Tile" Viewport="0,0,2,3" ViewportUnits="Absolute" Viewbox="0,0,5,5" ViewboxUnits="Absolute">
        <VisualBrush.Transform>
            <RotateTransform Angle="45" />
        </VisualBrush.Transform>
        <VisualBrush.Visual>
            <Canvas>
                <Path Data="M 0 0 L 0 10" Stroke="{Binding Path=Stroke, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Ellipse}}}" StrokeThickness="5"/>
            </Canvas>
        </VisualBrush.Visual>
    </VisualBrush>

Problem here is, I'm not able to set the Stroke property of the visal brush in app.xaml through the binding.

Need help. Thanks in advance

As a note, you do not need two DataTrigger for a boolean value. Just move the Setter of one of them directly to the Style (and thus make that a default value), and keep the other DataTrigger. Besides that, setting `UpdateSourceTrigger=PropertyChanged` on the Stroke and Fill Bindings is pointless. It only has an effect on TwoWay or OnewayToSource Bindings. — Clemens, Oct 23 '18 at 13:33
For the actual problem, Brushes don't form logical or visual trees, so the RelativeSource Binding won't work. — Clemens, Oct 23 '18 at 13:58
@Clemens, Then do you know any other way to achieve the desired solution?? — Tushar Gupta, Oct 23 '18 at 14:01
Not really. Such a HatchBrush resource usually has a predefined color. You may perhaps use it as an OpacityMask. — Clemens, Oct 23 '18 at 14:22

Clemens · Accepted Answer · 2018-10-23T14:31:21.747

You may perhaps use the Brush as an OpacityMask.

First, create a (simpler) DrawingBrush instead of a VisualBrush:

<DrawingBrush x:Key="HatchBrush" TileMode="Tile"
              Viewport="0,0,3,3" ViewportUnits="Absolute"
              Viewbox="0,0,2,2" ViewboxUnits="Absolute">
    <DrawingBrush.Drawing>
        <GeometryDrawing Geometry="M-1,2 L2,-1 M0,3 L3,0">
            <GeometryDrawing.Pen>
                <Pen Thickness="0.7" Brush="Black"/>
            </GeometryDrawing.Pen>
        </GeometryDrawing>
    </DrawingBrush.Drawing>
</DrawingBrush>

Then write a DataTrigger like this:

<DataTrigger Binding="{Binding IsHatchBrush}" Value="True">
    <Setter Property="OpacityMask" Value="{StaticResource HatchBrush}" />
</DataTrigger>

I converted my visual brush to drawing brush to make it create the visual tree which resolved my problem. Thanks for the help. — Tushar Gupta, Oct 24 '18 at 06:36

Access user control property in App.xaml style WPF

1 Answers1