WPF: How do I bind the color property of a gradientstop that is located in a controlTemplate in vb code?

Question

I need to do this in order to create a dynamic background brush for a custom control (inherits ContentControl). My custom control has two dependency properties: StartColor and EndColor. In the control template for the custom control, the control is wrapped in a border that's background is a RadialGradientBrush with gradient stops. one gradient stop's color is bound to StartColor and the other's is bound to EndColor. I have this WORKING in XAML, but I need to convert it to VB code. The border element of the control template in XAML is done with the following code:

<Style x:Key="{x:Type wpf:MyControl}" 
   TargetType="{x:Type wpf:MyControl}" 
   BasedOn="{StaticResource {x:Type ContentControl}}">
    <Style.Setters>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type wpf:MyControl}">

                      ...

                    <Border HorizontalAlignment="Stretch" 
                            x:Name="background" Width="Auto"
                            Grid.RowSpan="3" 
                            Opacity="0.9" 
                            CornerRadius="{TemplateBinding CornerRadius}">
                                <Border.Background>
                                    <Custom:RadialGradientBrush>
                                        <Custom:GradientStop Color="{Binding Path=EndColor, 
                                                            RelativeSource={RelativeSource TemplatedParent}, 
                                                            Mode=OneWay}" 
                                                            Offset="0.462"/>
                                        <Custom:GradientStop Color="{Binding StartColor, 
                                                            RelativeSource={RelativeSource TemplatedParent}, 
                                                            Mode=OneWay}" 
                                                            Offset="1"/>
                                    </Custom:RadialGradientBrush>
                                </Border.Background>
                            </Border>

                        ...

                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style.Setters>
</Style>

I tried to create the border in VB code as follows, but it did not work:

...
Dim backgroundBorder As New FrameworkElementFactory(GetType(Border))
        With backgroundBorder
            .Name = "background"
            .SetValue(Grid.RowSpanProperty, 3)
            .SetValue(Grid.OpacityProperty, 0.9)
            .SetBinding(Border.CornerRadiusProperty, New Binding("CornerRadius") With {.RelativeSource = New RelativeSource(RelativeSourceMode.TemplatedParent)})
        End With

        Dim backgroundBrush As New RadialGradientBrush()

        Dim startColorGradientStop As New GradientStop()
        startColorGradientStop.Offset = 1.0
        BindingOperations.SetBinding(startColorGradientStop, GradientStop.ColorProperty, New Binding("StartColor") With {.RelativeSource = New RelativeSource(RelativeSourceMode.TemplatedParent), .Mode = BindingMode.OneWay})
        backgroundBrush.GradientStops.Add(startColorGradientStop)

        Dim endColorGradientStop As New GradientStop()
        endColorGradientStop.Offset = 0.462
        BindingOperations.SetBinding(endColorGradientStop, GradientStop.ColorProperty, New Binding("EndColor") With {.RelativeSource = New RelativeSource(RelativeSourceMode.TemplatedParent), .Mode = BindingMode.OneWay})
        backgroundBrush.GradientStops.Add(endColorGradientStop)

backgroundBorder.SetValue(Border.BackgroundProperty, backgroundBrush)
...

Any ideas of how I can accomplish this in VB code?

Answer 1

Do you know the FrameworkElementFactory approach is not recommended anymore, according to MS? The recommended approach is to create any element/resource in code with XamlReader.Parse.