如何使用Generic.xaml中的样式将值从用户控件传递到自定义控件？

Question

In trying to make a simple customcontrol that accepts a string (Text), I am having difficulty passing values from the XAML to the customcontrol by way of the style in Generic.xaml.

The calling XAML does:

<wc:ccTestFigure Text="{Binding Text, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}" />

The ccTestFigure is defined as:

 public class ccTestFigure : FrameworkElement
{

    public static readonly DependencyProperty TextProperty =
        TextBlock.TextProperty.AddOwner(typeof(ccTestFigure));

    public String Text
    {
        get { return (String)this.GetValue(TextProperty); }
        set { this.SetValue(TextProperty, value); }
    }

    static ccTestFigure()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(ccTestFigure), new FrameworkPropertyMetadata(typeof(ccTestFigure)));
    }

    public ccTestFigure()
    {

        var typeface = new Typeface(
                        FontFamily,
                        FontStyle,
                        FontWeights.Normal,
                        FontStretches.Normal);

       ft  = new FormattedText(
               Text,
               System.Threading.Thread.CurrentThread.CurrentCulture,
               FlowDirection.LeftToRight,
               typeface,
               FontSize,
               Foreground);
    }


  protected override void OnRender(DrawingContext drawingContext)
    {
        base.OnRender(drawingContext);
        drawingContext.DrawText(ft, new Point());
    }

The Style in Generic.xaml does not like TemplateBinding, so I am at a loss how to pass the Text in from the usercontrol to the customcontrol, ccTestFigure.

The Style I have so far (which does not work) is:

 <Style TargetType="{x:Type local:ccTestFigure}">
    <Setter Property="Text" Value="{Binding Text, RelativeSource={RelativeSource Self}}"/>
</Style>

Where Text is a simple string.

I appreciate any help. Thanks in advance.

Answer 1

It looks like you are attempting to do something completely redundant, set the value of "Text" to itself.

The problem is just that you're not updating "ft" when "Text" changes. Add a property-change handler, and put the formatted-text stuff in there instead of the constructor:

public static readonly DependencyProperty TextProperty =
    TextBlock.TextProperty.AddOwner(typeof(ccTestFigure), new FrameworkPropertyMetadata(propertyChangedCallback: OnTextChanged));

private static void OnTextChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
{
    ((ccTestFigure)sender).UpdateText();
}

private void UpdateText() 
{
    var typeface = new Typeface(
                    FontFamily,
                    FontStyle,
                    FontWeights.Normal,
                    FontStretches.Normal);

   ft  = new FormattedText(
           Text,
           System.Threading.Thread.CurrentThread.CurrentCulture,
           FlowDirection.LeftToRight,
           typeface,
           FontSize,
           Foreground);
}

public ccTestFigure()
{
}

Answer 2

I post this as I know no other way to show the code. McGamagle is correct--just needed to make a few changes as below. Needed to add "AffectsRender" to display the text.

  public static readonly DependencyProperty TextProperty =
        TextBlock.TextProperty.AddOwner(typeof(ccTextFigure),
         new FrameworkPropertyMetadata(
            null,                                               
            FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure,    
            propertyChangedCallback: OnTextChanged              
            ));

In my case, I also needed AffectsMeasure to force a re-measuring for the parent scrollviewer.