unavailable component's customizations are removed from the .Designer.cs file

[AdmiralSnyder]

Environment

VS 18.4.1 pro/ent

.NET version

net10

Did this work in a previous version of Visual Studio and/or previous .NET release?

this was not an issue before we moved to .net 9/10, from Framework 4.8

Issue description

Hello,
when a usercontrol that is defined in another assembly that hasn't been built (i.e. the bin directory is empty) is used in a form, the designer removes the instance of that usercontrol without telling the developer, rendering nothing for that usercontrol into the Designer.cs file, apart from the declaration - this leads to nullreferenceexceptions at runtime, when the usercontrol is referenced in the form's source code, and ... well, that usercontrol is missing

Steps to reproduce

• create two projects in the solution, A and B, where B references A
• create a usercontrol in project A
• create a Form in project B, putting the usercontrol from project A onto it
• build, run, confirm the usercontrol is there.
• close VS, delete bin and obj folders to simulate a clear
• open VS, DO NOT REBUILD THE SOLUTION
• open the projectB.Form in the designer
• observe the usercontrol is missing

Diagnostics

there is no diagnostic, the missing usercontrol is just ignored. this is a huge problem, since it's not obvious when something is missing, within more complex forms for example. and there's no good way to track when this happened, either. the designer should at least create a (formerly golden) error bar, making it super obvious to the developer that something was missing.

[LeafShi1]

This issue is not a regression issue in .NET 11, it also exists in .NET 6.

.netFramework 4.8.1:

.net6.0(The same behaviour in .net7.0 - .net11.0):

[LeafShi1]

Transfer this issue to winform designer https://github.com/microsoft/winforms-designer/issues/6620