System.Windows.Forms.Control.ContextMenuChanged event is detected but cannot be raised when event handler is attached

[Olina-Zhang]

.NET version

.NET 10.0 SDK: 10.0.100-alpha.1.25074.11 + binaries built from Winforms main branch

Did it work in .NET Framework?

Yes

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

Yes, not repro in previous .NET versions, regressed from PR: #10913

Issue description

Our automation: take a sample, for button case, when calling all button' events, the event: button1.ContextMenuChanged is detected but cannot be raised when event handler is attached. Log as following:

        _*****Testing System.Windows.Forms.Control.ContextMenuChanged
        1. Verify event raised when event handler is attached
        FAIL: Event raised 0 times.
        FAIL: Expected sender = System.Windows.Forms.Button, Text: , but got 
        2. Verify event not raised after event handler is removed
        *****_

Manual testing: call button1.ContextMenuChanged event, cannot be raised

ContextMenuChangedIssue.mp4

Steps to reproduce

Mose of migrated automation cases are affected

Manual testing app:

WinFormsApp89.zip

[Tanya-Solyanik]

@Olina-Zhang - this is by design, please modify your test.