Capture RichTextBlock Hyperlink events

Question

I'm trying to capture the click event of Hyperlinks inside a dynamically generated RichTextBlock.

I'm dynamically generating the contents of a richtextblock and then applying them with XamlReader. The content can vary quite a bit, so I can't manually parse the xaml and hook up events at that point.

My basic idea is to, once the richtextblock is loaded, find all Hyperlinks in it and hook up their click event there. This is my current code:

    public class HookUpEvents()
    {
        foreach (var child in FindVisualChildren<Hyperlink>(richtxtblock))
        {
            child.Click += MyFunction;
        }
    }

    public static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
    {
        if (depObj != null)
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
            {
                DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
                if (child != null && child is T)
                {
                    yield return (T)child;
                }

                foreach (T childOfChild in FindVisualChildren<T>(child))
                {
                    yield return childOfChild;
                }
            }
        }
    }

Obviously, it isn't working. It looks like the FindVisualChildren function isn't returning any Hyperlinks. Any ideas on how I can achieve this?

Is the `RichTextBlock` also generated by `XamlReader`? If not, could I know why you load content by `XamlReader`? You have APIs do that right? — Sunteen Wu, Apr 12 '17 at 09:47
I load content with XamlReader because I'm using xslt to transform HTML to XAML. — user2950509, Apr 13 '17 at 15:28

Overrided · Answer 1 · 2021-01-16T14:02:24.343

Well, I'm sure late to the party, but RichTextBlock won't place his Blocks and their Inlines in VisualTree most of the time. To find all Inline-based elements (Run,Span,Bold etc.) you will need to loop through all content, by visiting each Block and subsequent Inline's. I would suggest something like this:

public static IEnumerable<T> GetAllTextElements<T>(this RichTextBlock rtb) where T : TextElement
{
    var result = new List<T>();

    var blocks = rtb.Blocks;

    foreach (var block in blocks)
    {
        if (block is T)
        {
            result.Add(block as T);
            continue;
        }

        var inlines = ((Paragraph)block).Inlines;

        var res = TraverseInline<T>(inlines);
        if (res != null && res.Any())
            result.AddRange(res);
    }

    return result;
} 

private static IEnumerable<T> TraverseInline<T>(IEnumerable<Inline> inlines) where T : TextElement
{
    var result = new List<T>();

    foreach (var item in inlines)
    {
        if (item is T)
        {
            result.Add(item as T);
            continue;
        }
        else if (item is Span) // first Inline derived class to have own `Inlines`
        {
            var spanItem = item as Span;
            var spanInlines = spanItem.Inlines;
            var results = TraverseInline<T>(spanInlines);

            if (results != null && results.Any())
                result.AddRange(results);
        }
    }

    return result;
}

So you can look for any TextElement-derived item with it. Usage would be something like:

var textHyperlinks = myRichTextBlock.GetAllTextElements<Hyperlink>();

This will do as far as you don't use InlineUIContainer. That type of Inline behaves differently, as you can put anything UIElement-based as it's Child property. In that case your initial approach should work.

score -1 · Answer 2 · answered Apr 06 '17 at 18:42

There's a couple of things here:

If you're trying to find the hyperlink inside of the RichTextBlock, its type is: Windows.UI.Xaml.Documents.Hyperlink. Not the type of the HyperLinkButton.

You can put the Click event handler in your text and then provide the handler method in your code behind file. If you dynamically generate text that looks like:

<Paragraph>
    Text with a
    <Hyperlink x:Name="link" Click="link_Click">link.</Hyperlink>
</Paragraph>

Feed that to the XamlReader, and put the following code in your code behind file:

private void link_Click(Windows.UI.Xaml.Documents.Hyperlink sender, Windows.UI.Xaml.Documents.HyperlinkClickEventArgs args)
{
    Debug.WriteLine("Handle link click, by: " + sender.Name);
}

Then it should connect up correctly at runtime. And you can do whatever you want on the Click event handler. Even if there are multiple links, you can name them differently and just use one click handler to process.

XamlReader doesn't support inline events like that: https://learn.microsoft.com/en-us/uwp/api/Windows.UI.Xaml.Markup.XamlReader — user2950509, Apr 06 '17 at 22:23

Capture RichTextBlock Hyperlink events

2 Answers2