I am writing a website in VS2015 using the ASP.NET Preview template. Unfortunately, Dropbox has added a bunch of .dropbox.attr files in each folder of my projec
In a DNX project in visual Studio 2015 the solution explorer does not use the project.json to determine what is shown. The "exclude" properties in project.json are used by dnx to determine which folders/files should be excluded from compilation or publishing but this does not affect Visual Studio's solution explorer.
Generally speaking "everything" is shown but that isn't exactly true as VS excludes certain folders (such as .git, .vs, artifacts, etc). It also adds back others (i.e. bower components is excluded by default from compilation but VS adds it back as a meta folder under dependencies). The "filter" for Solution Explorer is not exposed to the user so it can't be edited or changed by configuration file.
Your best bet would be to request via user voice that some method of configuration be added. Really the functionality is already there it just needs to be made customizable by the user.