In my solution I have three projects: Console application, class library, and a website project.
The Show All Files button is visible on the console and class library proje
if you click on solution name in "solution explorer" maybe you will can't see "Show all files" button. because maybe added F# or website project in solution.
if you want see "Show all files" button, you must click on project name which is C# or native C++ or C++.net.