Validation adorner does show up for controls with initial errors inside an Expander

[batzen]

• .NET Core Version: All
• Windows version: 1903
• Does the bug reproduce also in WPF for .NET Framework 4.8?: Yes

Problem description:
This issue occurs on controls that "hide" their child controls. These controls are, for example, Expander and TabControl.

Actual behavior:
Validation adorner does not show up for not yet visible controls with validation errors.

Expected behavior:
Validation adorner should show up as soon as controls get visible if they were not visible before but have validation errors.

Minimal repro:

• Create an object that implements INotifyDataErrorInfo
• Always return true in HasErrors
• Always return some text in GetErrors
• Create a property on that object
• Create a TextBox and bind to the property on the object
• Place the TextBox inside a collapsed (IsExpanded=False) Expander
• Expand the Expander, no validation adorner is shown

[grubioe]

To be considered when all tests are ported

[batzen]

@grubioe any news on this?

[grubioe]

@fabiant3 can provide the latest status.

[pchaurasia14]

@dipeshmsft - Here is the repro for this issue.
https://github.com/pchaurasia14/validationadornerissue

[h3xds1nz]

This was fixed in #1167, hence closing.