What's the best way to prevent losing TextBox focus when there is a validation error?

Question

I\'ve messed around with PreviewLostKeyboardFocus which almost gets you there. I\'ve seen a couple of implementations using LostFocus, but that just f

Answer 1

To add onto Ray's answer:

UpdateSource is called like so:

BindingExpression be = userTextbox.GetBindingExpression(TextBox.TextProperty);
be.UpdateSource();

Also, as an alternative you can set the text box binding to:

UpdateSourceTrigger = "PropertyChanged";

The latter will cause a continuous check, whereas the former will check when needed (performant).