WPF TextBlock highlight certain parts based on search condition

Question

I have TextBlock that has Inlines dynamicly added to it (basically bunch of Run objects that are either italic or bold).

In my application I have search function.

Answer 1

I took dthrasers answer and took out the need for an XML parser. He does a great job explaining each of the pieces in his blog, However this didn't require me to add any extra libraries, here's how I did it.

Step one, make a converter class:

class StringToXamlConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        string input = value as string;
        if (input != null)
        {
            var textBlock = new TextBlock();
            textBlock.TextWrapping = TextWrapping.Wrap;
            string escapedXml = SecurityElement.Escape(input);

            while (escapedXml.IndexOf("|~S~|") != -1) {
            //up to |~S~| is normal
            textBlock.Inlines.Add(new Run(escapedXml.Substring(0, escapedXml.IndexOf("|~S~|"))));
            //between |~S~| and |~E~| is highlighted
            textBlock.Inlines.Add(new Run(escapedXml.Substring(escapedXml.IndexOf("|~S~|") + 5,
                                      escapedXml.IndexOf("|~E~|") - (escapedXml.IndexOf("|~S~|") + 5))) 
                                      { FontWeight = FontWeights.Bold, Background= Brushes.Yellow });
            //the rest of the string (after the |~E~|)
            escapedXml = escapedXml.Substring(escapedXml.IndexOf("|~E~|") + 5);
            }

            if (escapedXml.Length > 0)
            {
                textBlock.Inlines.Add(new Run(escapedXml));                      
            }
            return textBlock;
        }

        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException("This converter cannot be used in two-way binding.");
    }

}

Step two: Instead of a TextBlock use a ContentBlock. Pass in the string (you would of used for your textBlock) to the content block, like so:

Step three: Make sure the text you pass includes |~S~| before and |~E~| after the text part you want to be highlighted. For example in this string "my text |~S~|is|~E~| good" the is will be highlighted in yellow.

Notes:
You can change the style in the run to determine what and how your text is highlighted
Make sure you add your Converter class to your namespace and resources. This might also require a rebuild to get working.