Touch bug/issue with ShowDialog and TextBox

_This issue has been moved from [a ticket on Developer Community](https://developercommunity.visualstudio.com/content/problem/890778/touch-bugissue-with-showdialog-and-textbox.html)._

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Hello I'm developing a WPF application to be used with touch devices (Running Win 10 full).

There is one scenario where the touch stops responding as expected.
If I have a TextBox and open a dialog (ShowDialog()) then the dialog won't handle any touch and will ignore the user:

A) 1 touch ignored - if using single touch driver.

B) 10 touches ignored - if using multi touch driver.

And after that it starts responding normally again.

I have attached a video show casing this issue and also a test project so you can easily replicate (using Windows Simulator w/ touch or a touch monitor)
In the video you can see that when opening the dialog through a button it responds as expected but if opened through a TextBox it will then have a touch issue.

textbox-showdialog-touch-issue.mp4

ms-wpf-testtouchdialogs.zip

The code being used is just this:

        private void TextBox_PreviewMouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)

        {

            // This cause touch issues within the dialog.

            // (1 touch ignored w/ single touch monitor/driver - 10 touches ignored w/ multi touch monitor/driver)

            new DialogWindow(). ShowDialog();

        }


private void Button_Click(object sender, RoutedEventArgs e)

        {

            new DialogWindow(). ShowDialog();

        }

Windows 10
VS 2019
.NET 4.6.1 (but it was also tested with 4.8, exactly same issue)

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### Original Comments

#### Visual Studio Feedback System on 1/20/2020, 06:41 PM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

#### Visual Studio Feedback System on 1/30/2020, 01:12 PM:

This issue is currently being investigated. Our team will get back to you if either more information is needed, a workaround is available, or the issue is resolved.

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### Original Solutions
(no solutions)