I do not know what happened with my code. I probably inadvertently deleted one half of a pair of braces '[]' or parens '()' without realizing it, snooping around in the code just to look. A missing brace is what the MS site says probably causes this error, but the compiler should not point me to the XML file.

I deleted the project and recreated it, clearly not an option if this happens in a large project with many forms and classes.

Thanks for your efforts.