What does it mean when Visual Studio tells me my project doesn't support code?

Answer 1

I don't believe that the problem is a lack of supporting code. It's more likely that the code in ReportForm.cs or ReportForm.designer.cs is not parsable by the WinForms designer class. You can verify this by deleting all of your code and type in something very simple and reload the designer.

Example:

public class ReportForm(){ 
  public ReportForm(){}
}

Answer 2

Duplicate question: look here. In short: VS bug.

Answer 3

I've come across this one when I've renamed a form then closed and re-opened VS. The error is thrown and I can't see the designer. The remedy for me was checking to make sure the project form is looking for my newly named form and not the old name, if it is the old name then just delete it and add->existing item.

All should be good from that point.