Скачать или смотреть How to Fix the TextChanged Event Issue in Your Custom WPF TextBox User Control

Discover how to resolve the issue where changing text in your custom WPF TextBox user control does not reflect changes as expected.
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This video is based on the question https://stackoverflow.com/q/69227071/ asked by the user 'Manolo Martinez' ( https://stackoverflow.com/u/16572649/ ) and on the answer https://stackoverflow.com/a/69228176/ provided by the user 'Groger' ( https://stackoverflow.com/u/12297767/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the Text Binding Issue in a Custom WPF TextBox User Control

Creating a custom TextBox user control in WPF can be a rewarding experience. However, it can also lead to some frustrating issues, especially when it comes to data binding. One common problem developers encounter is when the TextChanged event does not reflect the changes made to the text input. In this guide, we will explore why this happens and how you can resolve the issue effectively.

Understanding the Problem

Imagine that you have designed a custom WPF TextBox user control, and you’ve noticed a peculiar issue: as you update the content of the TextBox, it seems to always return the default text specified in the XAML instead of the new input.

For instance, if your placeholder text is "Input a keyword to filter..." and you type "test", calling textbox.Text still gives you "Input a keyword to filter...". This can be quite puzzling and stands in the way of creating a functional user experience.

Analyzing the Source Code

To understand why this issue occurs, let’s break down the specific parts of the provided SearchBox code:

[[See Video to Reveal this Text or Code Snippet]]

Inheritance: The class inherits from UserControl rather than TextBox. Consequently, the Text property in your SearchBox control is separate from the internal TextBox's text property.

Data Binding: Your control's Text property does not automatically bind to the TextBox within the control unless explicitly programmed to do so. When you modify the internal TextBox, the Text property remains unchanged.

The Solution

To ensure that the text entered by the user is correctly reflected in your custom control, follow these steps:

Step 1: Expose the Internal Text Property

Modify your class to expose the internal TextBox's Text property directly. This ensures that whenever the text is changed in the TextBox, it can be accessed from the SearchBox control. Here’s how you would do that:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Adjust the XAML

Your usage should look something like this in XAML:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Test the Control

After implementing the above changes, test the SearchBox control. When the user types new text, accessing searchBox.Text should now yield the fresh content entered in the TextBox.

Conclusion

By properly linking your Text property to the internal TextBox within your SearchBox control, you can ensure that the user's input is accurately captured and reflected. This simple adjustment not only resolves the TextChanged event issue but also enhances the usability of your custom control.

If you encounter similar issues in the future, remember that understanding the separation between your custom properties and the internal text properties of controls is crucial in WPF development. Happy coding!