I just published my latest article about an issue I had no later than last week.
I wanted to use a generic form but the designer (very useful in Windows Forms) was always reporting a strange error even if the compilation was not reporting any issues.
If you ever tried, you surely had the issue.
If you never tried, read on, this is a great feature and the workaround to make the designer is really easy!
You can read it from http://emoreau.com/Entries/Articles/2016/02/Issues-with-Generic-Windows-Forms-inheritance-and-the-solution.aspx