How to register new item in the "Add -> New Item.." solution explorer dialog

Question

I have created Visual Studio 2012 Package Project (from VS2012 SDK) with my own Custom Editor. It works fine. Editor is associated with solution files with *.myext extensions. Now, I would like to be able to create such a *.myext files with taking advantage of Add -> New Item.. option from context menu in Solution Explorer of VS2012. Thereafter, what is important, this additional functionality should create two files at one, similarly as it is performed by EF Entity Data Designer, WinForms designer, Resources designer, etc. First file with main editable content which is modified by Custom Editor (*.myext) and contains design schema, and the second file which is auto-generated and contains output (in my case XML) data (*.myext.xml.).

How can I register file type and implement that functionality?

Answer 1

This article shows how to add Items to the Add New Item Dialog Boxes. I'm sure it will be easy to find possibility to create two files instead of one.
Or you can add you own menu item to Add menu using VSPackage.