I got this error today and I was shocked… The InnerException was saying something like this
Only one <configSections> element allowed per config file and if present must be the first child of the root <configuration> element.
Well I had ONLY 1 configSections element in my App.config…. After loads of hair pulling I discovered its because the <configSections> element has to be defined as the first element in the App.config. Well thanks for the very useful exception message!
I hope this helps whoever encounters the same error…