Using VS 2017 I found that it has grown very attached to one C# file and will constantly decorate it with:
<SubType>Component</SubType>
int the project file.
The file is just a plain vanilla C# file that has absolutely nothing special; but the IDE treats it as if it was a form.
When I remove this tag, it re-appears. When I replace the word Component by anything else, it comes back.
It does it only to this file.
A google search shows that this is a bug since VS 2015 and it was reported to Microsoft but they never fixed it; Now, with VS 2017, it's still present so I'm not hoping they'll ever fit it, but I'm curious if anyone has found a workaround for this problem?