DialogHost doesn't return current value when dialog is accepted from keyboard.

DialogHost doesn't return current value when dialog is accepted from keyboard.

MaterialDesignThemes v. 4.0.0

Repository with example: https://github.com/lszczygielek/MaterialDesignInXamlToolkit-DialogHost-Focus

@Keboo wrote about it on Gitter:

I wrote a small test to also show the issue here. I did write a little UI test to reproduce the issue as well: https://github.com/Keboo/MaterialDesignInXamlToolkit/tree/dialogHostDoesNotUpdate
If anyone wants to have a go at addressing it that would be a good start. I spent a little time looking at it, and it seems like it may be a little difficult with timing to address it within the dialog host as you need to trigger the lost focus event and wait for the binding to update. This may end up being something that needs to be addressed outside of this library.
It also appears this is somewhat expected as several other people have run into similar use cases. https://www.thomasclaudiushuber.com/2008/05/02/lostfocus-textbox-vs-buttons-isdefault-property/

Start with the linked DialogHost-Focus example and the UI test in the dialogHostDoesNotUpdate branch to reproduce keyboard acceptance in MaterialDesignThemes 4.0.0. Trace DialogHost's handling of focus and binding updates, then verify that accepting the dialog returns the current value shown in the control.