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Form is removed from Application.OpenForms after RecreateHandle

See original GitHub issue

.NET version

.Net6, .Net7 checked.

Did it work in .NET Framework?

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

I checked only .Net6, .Net7 but according to the code, problem exist in all versions (.net framework too).

Issue description

While working on https://github.com/dotnet/winforms/issues/3606 I found that after calling to RecreateHandle, the form is completely removed from Application.OpenForms.

The form is added to Application.OpenForms in two cases:

OnLoad.
SetVisibleCore(true) 🤔

The form is removed from Application.OpenForms in two cases:

OnFormClosed.
OnHandleDestroyed 🤔🤷‍♂️

Here we clearly see that after RecreateHandle we will completely lost our form from Application.OpenForms 😦 We call RecreateHandle for the form in several cases (ShowInTaskbar \ RightToLeft change etc…). I still can’t say for sure how much duplication of the Application.OpenForms.Remove call in OnHandleDestroyed is necessary.

Steps to reproduce

FormCloseTest.zip

Build.
Run.
Press button2 => Application.OpenForms will contains 3 forms (main, mdiParent and mdiChild).
Press button3 => Application.OpenForms will contains 1 form - main.

Issue Analytics

State:
Created 5 months ago
Comments:8 (7 by maintainers)

Top GitHub Comments

2reactions

elachlancommented, Apr 24, 2023

Probably, but I’d try and keep them as separate commits and make sure the merge isn’t done via a squash.

1reaction

MandiMancommented, May 31, 2023

Verified this on .NET 8.0 TP build: 8.0.100-preview.5.23276.4, issue was fixed, test result is same as above video.

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