Question

I attempted to open a C#/VB form in designer mode, and instead of the form, I got an ugly error message saying ‘The path is not of a legal form’. This form used to work! What happened?

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Thanks to all who have answered. This question is a problem I hit a while back, and I struggled with it for a long time, until I found the answer, which I posted below in order to help other people who might have hit this problem.
Thanks!

Answer 1

I don’t know what this error message means, but it seems to be associated with third-party controls on the form. Anyway, the solution is almost as absurd as the problem:

1. Close the designer/error message.
2. Open the form code.
3. Right-click on the form code and select ‘View Designer’.

Presto! The designer opens!