WPF: How can I update Text in TextBox in code without losing binding information?

Question

I created a validating WPF user control, derived from TextBox.

The Text property in my TextBox is bound using something like <my:MyTextBox Text={Binding ..., Mode=OneWay}. The user may update the displayed text therein, so I can further process the updated text.

When the user enters invalid text, I want to re-enter valid data into my custom TextBox using code like Text = _validText;. But when I do that, the original Binding is lost for the Text property (of course).

How can I update a TextBox's Text in code without losing the original binding information?

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(PS: Original question was posted here. I closed the original question now after realizing that assigning text to the Text property obviously overwrites the original binding information.)

Answer 1

Thanks for all your replies.

I wanted to keep invalid characters from being typed into the front-end, so the view-model could have kept their original data type (e.g. int). When the TextBox would have lost focus, I would have manually updated the source (using BindingExpression::UpdateSource())

It doesn't look like this is possible.

So, I changed all view-model properties to string and switched to Mode=TwoWay. And I manually convert data types later then.

Answer 2

Change the Mode to TwoWay.

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~~Bonnie DeWitt [MVP since 2003]
[http://geek-goddess-bonnie.blogspot.com]1