What is the "Could not find the type System.Collections.Generic.List" in .NET Designer?

Question

I have a WinForms project that I have had for some time, and now suddenly I can no longer open the constructor, and when I try to open the constructor, I get an error

could not find type 'System.Collections.Generic.List'

All the code builds just fine, but I can no longer use the constructor, and I don’t know what happened, and I don’t know where to look for a solution to the problem. Has anyone ever come across this or had any understanding?

Answer 1

Just in case, someone is interested, that's what happened.

- InitializeComponent Forms, . , , .

, , Generics InitializeComponent. , , , , InitializeComponent.

Answer 2

. Designer. , .

Answer 3

, .NET?

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Answer 4

. , .

Answer 5

. :

1) .designer.cs.

2) , - , .

, System.Collections.Generic form.cs, form.designer.cs , - .