C# WPF RichTextBox - Hyperlinks

Question

I'm looking for a way to autodetect hyperlinks in RichTextBoxes in WPF (or if there is a smiliar control that's suitable for it, I'll take that...just needs to be a TextBox).

I'm aware of these solutions: - Clicking HyperLinks in a RichTextBox without holding down CTRL - WPF - WPF Dynamic HyperLinks RichTextbox

But my problem is, that I'm using two-way-binding in order to add dynamically RichTextBoxes to an ItemControl. My DataTemplate looks like this:

<RichTextBox IsDocumentEnabled="True" IsReadOnly="True">
   <FlowDocument>
      <Paragraph>
           <Run Text="{Binding MyDataText}"/>
     </Paragraph>
  </FlowDocument>
</RichTextBox>

When I want to include clickable hyperlinks, I'd need to add them with

<Paragraph>
    <Hyperlink> 
    https://stackoverflow.com
    </Hyperlink>
<Paragraph>

But since I'm using data binding with only the text as shown above - and I'm tbh not aware of another solution - with the defined Data Template, I can't use that. The point is also that I need to mix normal text AND hyperlinks in one RichTextBox.

I'd appreciate any help, thanks!

Answer 1

You can use an attached property to enable data binding to the RichTextBox . Then implement a IValueConverter to convert from string to the appropriate FlowDocument after checking the type of the string value:

RichTextBox.cs

public class RichTextBox : DependencyObject
{
  public static readonly DependencyProperty DocumentSourceProperty = DependencyProperty.RegisterAttached(
    "DocumentSource",
    typeof(FlowDocument),
    typeof(RichTextBox),
    new PropertyMetadata(default(string), RichTextBox.OnDocumentSourceChanged));

  public static void SetText([NotNull] DependencyObject attachingElement, FlowDocument value) =>
    attachingElement.SetValue(RichTextBox.DocumentSourceProperty, value);

  public static string GetText([NotNull] DependencyObject attachingElement) =>
    (FlowDocument) attachingElement.GetValue(RichTextBox.DocumentSourceProperty);


  private static void OnDocumentSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
  {
    if (!(d is System.Windows.Controls.RichTextBox richTextBox))
    {
      throw new ArgumentException($"Wrong type.\nThe attaching element must be of type {typeof(System.Windows.Controls.RichTextBox)}.");
    }

    Application.Current.Dispatcher.InvokeAsync(
      () => richTextBox.Document = (FlowDocument) e.NewValue,
      DispatcherPriority.DataBind);
  }
}

StringToFlowDocumentConverter.cs

[ValueConversion(typeof(string), typeof(FlowDocument))]
public class StringToFlowDocumentConverter : IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  {
    if (value is string stringValue)
    {
      return stringValue.StartsWith("http", StringComparison.OrdinalIgnoreCase)
        ? CreateHyperlinkDocument(stringValue)
        : CreateTextDocument(stringValue);
    }

    return Binding.DoNothing;
  }

  public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  {
    throw new NotSupportedException();
  }

  private FlowDocument CreateHyperlinkDocument(string url)
  {
    return new FlowDocument(new Paragraph(new Hyperlink(new Run(url))));
  }

  private FlowDocument CreateTextDocument(string text)
  {
    return new FlowDocument(new Paragraph(new Run(text)));
  }
}

MainWindow.xaml

<Window>
  <Window.Resources>
    <StringToFlowDocumentConverter x:Key="StringToFlowDocumentConverter" />
  </Window.Resources>

  <RichTextBox RichTextBox.DocumentSource="{Binding MyDataText, Converter={StaticResource StringToFlowDocumentConverter}" />
</Window>