Narrator cannot announce the content in RichTextBox

[dmitrii-drobotov]

.NET version

7.0 Preview 6

Did it work in .NET Framework?

No

Did it work in any of the earlier releases of .NET Core or .NET 5+?

This is a regression issue (see #3455). It does not repro in .NET 6.0.

Issue description

Narrator should announce the content in RichTextBox.
Expected behavior (.NET 6):

Actual behavior (.NET 7 Preview):

Steps to reproduce

1. Add a RichTextBox control on a form
2. Enter any text content into RichTextBox, then start Narrator and focus on RichTextBox and observe Narrator behavior

[John-Qiao]

Verified with 7.0.100-rc.1.22371.5 from main branch, this issue has been fixed that Narrator announces the content in RichTextBox now.