Make a Part of Text Bold inside TextBlock

Question

I know that we can use <Run> in XAML to achieve what I am asking :

<TextBlock.Inlines>
    <Run Text="This is" />
    <Run FontWeight="Bold" Text="Bold Text." />
</TextBlock.Inlines>

Also I can do it in code behind as follows:

TextBlock.Inlines.Add(new Run("This is"));
TextBlock.Inlines.Add(new Bold(new Run("Bold Text.")));

But my problem is something different:

Suppose I have following Text in my database:

This is <b>Bold Text</b>.

Now, my Textblock is bound to a field that contains the above text in database.

I want the text between <b> and </b> to be bold. How can I achieve this?

Answer 1

It looks like you want to replace your custom formatting with <Bold> - see TextBlock for more info. Sample from the article:

<TextBlock Name="textBlock1" TextWrapping="Wrap">
  <Bold>TextBlock</Bold> is designed to be <Italic>lightweight</Italic>,
  and is geared specifically at integrating <Italic>small</Italic> portions
  of flow content into a UI.
</TextBlock>

One approach is to re-format string to match what TextBlock expects.

If you have HTML input - parse the text with HtmlAgilityPack first and than walk though resulting elements and construct string with b-elements replaced with text wrapped <Bold> and similar to other formatting.

If database content is known to have only valid begin/end pairs (not random HTML) you may even get away with basic String.Replace : text = text.Replace( "", "")`.

If you have you own custom formatting (like *boldtext*) you'll need to invent custom parser for that.

Answer 2

You can subscribe to TargetUpdated event:

 void textBlock_TargetUpdated(object sender, DataTransferEventArgs e)
 {
        string text = textBlock.Text;

        if (text.Contains("<b>"))
        {
            textBlock.Text = "";
            int startIndex = text.IndexOf("<b>");
            int endIndex = text.IndexOf("</b>");
            textBlock.Inlines.Add(new Run(text.Substring(0, startIndex)));
            textBlock.Inlines.Add(new Bold(new Run(text.Substring(startIndex + 3, endIndex - (startIndex + 3)))));
            textBlock.Inlines.Add(new Run(text.Substring(endIndex + 4)));
        }
    }

and XAML for the TextBlock:

<TextBlock x:Name="textBlock" Text="{Binding NotifyOnTargetUpdated=True}"></TextBlock>