自动突出显示 TextBox 或 RichTextBox 中的部分文本

Question

Is it possible to highlight a part of a text without selecting this part of the text preferably with a different color in Textbox or Rich TextBox? In fact, I mean, a part of the text is highlighted by another color differing from the color assigned for text selection. To clarify, I have attached an image showing this behavior. (The image is from a website, not WPF). The bold and dark green part is a text which is just highlighted, and the gray region is a selected part.

Answer 1

Using the RichTextBox element allows for more styling options which, to my knowledge, aren't available for the regular TextBox element.

Here is an approach that I have created:

// Generate example content
FlowDocument doc = new FlowDocument();

Run runStart = new Run("This is an example of ");
Run runHighlight = new Run("text highlighting in WPF");
Run runEnd = new Run(" using the RichTextBox element.");

// Apply highlight style
runHighlight.FontWeight = FontWeights.Bold;
runHighlight.Background = Brushes.LightGreen;

// Create paragraph
Paragraph paragraph = new Paragraph();
paragraph.Inlines.Add(runStart);
paragraph.Inlines.Add(runHighlight);
paragraph.Inlines.Add(runEnd);

// Add the paragraph to the FlowDocument
doc.Blocks.Add(paragraph);

// Apply to RichTextBox
YourRichTextBoxHere.Document = doc;

View Screenshot

Answer 2

I found this article to be helpful.

Highlight Searched Text in WPF ListView

While the article is about highlighting searched text in a ListView, I have easily adapted it in my own code to work with pretty much any control.

Starting with the control you pass in, it will recursively look for TextBlock s and will find the text you want, extract it as an inline, and will change it's Background / Foreground properties.

You can easily adapt the code to be a behavior if your want.

Here is an example:

private void HighlightText(object controlToHighlight, string textToHighlight)
{
    if (controlToHighlight == null) return;

    if (controlToHighlight is TextBlock tb)
    {
        var regex = new Regex("(" + textToHighlight + ")", RegexOptions.IgnoreCase);

        if (textToHighlight.Length == 0)
        {
            var str = tb.Text;
            tb.Inlines.Clear();
            tb.Inlines.Add(str);
            return;
        }

        var substrings = regex.Split(tb.Text);
        tb.Inlines.Clear();

        foreach (var item in substrings)
        {
            if (regex.Match(item).Success)
            {
                var run = new Run(item)
                {
                    Background = (SolidColorBrush) new BrushConverter().ConvertFrom("#FFFFF45E")
                };

                tb.Inlines.Add(run);                            
            }
            else
            {
                tb.Inlines.Add(item);
            }
        }
    }
    else
    {
        if (!(controlToHighlight is DependencyObject dependencyObject)) return;

        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(dependencyObject); i++)
        {
            HighlightText(VisualTreeHelper.GetChild(dependencyObject, i), textToHighlight);
        }
    }
}

I hope this is helpful!