How to link InkToolbar to an InkCanvas which is inside CustomControl?

Question

I am creating a CustomControl which contain InkCanvas . Now the problem is How do I link InkToolbar (which is outside the CustomControl) to an InkCanvas (which is inside the CustomControl)?

Solution Tried:

I tried to get the InkCanvas outside the CustomControl using below code but It is not working .

Here is my code (With the solution I tried which is not working ):

//In CustomControl Code Behind
InkCanvas PATH_INK_CANVAS;

protected override void OnApplyTemplate()
{
    PATH_INK_CANVAS = GetTemplateChild<InkCanvas>("PATH_INK_CANVAS");
}

T GetTemplateChild<T>(string elementName) where T : DependencyObject
{
    var element = GetTemplateChild(elementName) as T;
    if (element == null)
        throw new NullReferenceException(elementName);
    return element;
}

public InkCanvas InkCanvas
{
    get { return PATH_INK_CANVAS; }
}

public static readonly DependencyProperty InkCanvasProperty =
    DependencyProperty.Register("InkCanvas", typeof(InkCanvas), typeof(RichInkTextBox), new PropertyMetadata(0));

//In CustomControl XAML
<Style>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <Grid Name="MainGrid" Width="{TemplateBinding Width}" Height="{TemplateBinding Height}">
                    <InkCanvas Name="PATH_INK_CANVAS" Canvas.ZIndex="-1"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

//In Page
<local:CustomControl x:Name="MyCustomControl"/>
<InkToolbar Grid.Row="0" TargetInkCanvas="{x:Bind MyCustomControl.InkCanvas}"/>

Answer 1

I don't think that's the right syntax to define a read-only dependency property. Try something like the following instead -

public InkCanvas InkCanvas
{
    get => (InkCanvas)GetValue(InkCanvasProperty);
    private set => SetValue(InkCanvasProperty, value);
}
public static readonly DependencyProperty InkCanvasProperty = DependencyProperty.Register(
    "InkCanvas", typeof(InkCanvas), typeof(InkCanvasWrapper), new PropertyMetadata(null));

Also, make sure you set the Mode of the x:Bind to OneWay as the default value of the InkCanvas dependency property is null (you are setting the default value to 0 which is wrong).

<InkToolbar Grid.Row="0" TargetInkCanvas="{x:Bind MyCustomControl.InkCanvas, Mode=OneWay}" />