Changing the background color of text in a WPF TextBox

Learn how to change the background color of text in a WPF TextBox without affecting the entire TextBox. Explore alternative options like TextBlock and RichTextBox for more flexibility.
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This video is based on the question https://stackoverflow.com/q/72259792/ asked by the user 'SideSky' ( https://stackoverflow.com/u/12273101/ ) and on the answer https://stackoverflow.com/a/72262122/ provided by the user 'BionicCode' ( https://stackoverflow.com/u/3141792/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Changing the Background Color of Text in a WPF TextBox: A Comprehensive Guide

In the world of WPF (Windows Presentation Foundation), developers often face the challenge of customizing controls to enhance user experience. One common requirement is the ability to change the background color of text within a TextBox — without altering the entire TextBox's background color. Unfortunately, the TextBox in WPF does not support this feature natively. So, what are our options? Let’s explore some alternative solutions that could fulfill this need.

Understanding the Limitation

First and foremost, it’s important to note that a standard TextBox does not support rich text formatting or colored text. This means if you set a background color, it applies to the whole control. To achieve the desired functionality, you often need to look at two alternatives: TextBlock and RichTextBox. Let’s break down each option.

Option 1: Using TextBlock for Rich Text

TextBlock is more flexible when it comes to display formatting, allowing you to use multiple textual runs with distinct styles. Here’s how you can implement it:

Directly Handling Text Elements

You can create a TextBlock and define different text segments as separate Run elements. This is particularly useful for static text.

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Finding Specific Text Dynamically

In cases where you need to apply background color dynamically based on specific text values, you might use the following approach:

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Dynamic Highlighting with MultiBinding

To highlight text dynamically with multiple colors, you can use a MultiBinding along with a converter. Below is an example structure for your converter and control setup:

HighlightInfo Structure: This defines your highlight ranges and colors.

TextToInlineConverter Class: This class handles the logic for converting text into inline visual elements for the TextBlock.

XAML Setup: Bind your TextBlock to its properties using MultiBinding.

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The complete implementation will involve more detailed code concerning how the TextToInlineConverter processes the text and applies chosen styles.

Option 2: Using RichTextBox for User Input

If you need to allow users to input formatted text, RichTextBox is your best bet. Here’s a simple way to set up a RichTextBox that supports highlighting:

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And you can populate it dynamically as follows:

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Conclusion

While the WPF TextBox doesn’t support changing the background color of parts of its text natively, using TextBlock or RichTextBox can help you achieve the desired output. By employing the outlined approaches, you can create dynamic and visually appealing text displays in your WPF applications. Happy coding!

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