I run vs2015 (oxygene) and vs2017 (csharp) at the same time. If I create a new, empty website and add a webform I get a dialog in oxygene like this:
Now if you select the lower option the website will run in the browser (if you have no mistakes).
But, if you select the top option and add a new ‘web.config’ file, then you have problems. vs2017 creates a correct ‘web.config’ file by default so you do not see this dialog. The trouble is that the web.config file created by elements is empty. This generates an error called ‘Root element is missing’.
What I did is copy and paste from the csharp project/website to the empty web.config file ans it ran fine. There was one warning however. This line generates a warning: ‘targetFramework is not allowed’. It runs however. Why is this supported in csharp and not in oxygene?