Error Screen When Opening VB Form Design Module

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Error Screen When Opening VB Form Design Module

njl100 41

In Visual Studio 2019 Community Edition I have started getting the attached error screen when I open the form design module for 1 of my forms. This has just started appearing for no apparent reason. The variable concerned is a User Control I created in the app a few years ago and have not touched since and I haven't a clue how to fix this. If I ignore the error message and go into the form it looks ok, the application will build ok and it runs ok with no obvious errors on this particular form.
I saved a snapshot of the solution about a year ago so restored that onto my system and did a code compare both for the designer modules for the user control and for the form on which it is happening and they are identical to those on the current system. The error screen does not occur when I open this form on this old version of the solution.

Can anyone suggest what I need to do to make this problem go away.

TIA

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Answer 1

Michael Taylor 61,096

Couple of things come to mind.

1) If the UC type is in the same project then the project must build before the designer can load it properly. Often it is better to keep the controls in a separate project so the designer can load them even if the main app doesn't compile.
2) Are you using the new Winforms designer? If so switch to the legacy designer and see what happens. It could be a bug in the new designer.

njl100 41 Reputation points

2021-07-28T17:13:29.013+00:00
Thanks for replying

I will look at putting the uc into a separate project. I'm a bit of a novice so may take me a little while.

How do I know if I am using the new Winforms designer. When I create a form I just select Project / Add Form (Windows Forms) and specify the name and go from there. When I double click on the form in the Solution Explorer it opens the form in design mode ( tab says frmName.vb [Design]).
Michael Taylor 61,096 Reputation points

2021-07-28T17:21:46.843+00:00

In the menu go to Tools\Options then Environment\Preview Features then go to bottom and find Use the preview Windows Forms designer. Note that if your app is a .NET Framework app then this wouldn't have any impact.
Michael Taylor 61,096 Reputation points

2021-07-28T17:22:11.767+00:00

Also, sometimes just compiling the code (especially if you just downloaded it) before opening the designer solves the problem.
njl100 41 Reputation points

2021-07-29T08:40:14.923+00:00

Compiling before opening the designer seems to have done the job. I did notice prior to doing this that the offending user controls were not in the list of controls for the form on the Properties panel. Now they are there!

Thanks for your help.

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Error Screen When Opening VB Form Design Module

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