Sorry this forum is not for syntax and general coding discussion.

Visual Micro does have some options such as add>item that creates cpp/h class as an example, there is also a File>New example and a lot of the arduino core also uses classes so you can look at those.

You might question why you have defined Foo twice.

I see. That function is just a helper function creates classes in a similar way to many that are used in the arduino cores.

You can create classes however you like. You can also use the standard visual studio "add new item > class" which uses a wizard to allow you to specify options. As long as all the options are arduino/gcc compatible then they are fine to use.

You can also add your own "new item" templates that create file(s) containing whatever you like. It's worth reading up on Visual Studio Item templates they are very powerful.

The example that you mention allows users to more obviously create multiple versions of the class. For example if you had ButtonClass and your project had 4 buttons you could create 4 instances very easily.

ButtonClass Button1;
ButtonClass Button2;
ButtonClass Button3;
ButtonClass Button4; 

The example works similar to HardwareSerial in the avr core which might provide Serial, Serial1, Serial2 etc. all based on HardwareSerial.

There are plenty of Gcc C++ combinations and Visual Micro has no control over how any are compiled it just passed source code paths to the compiler specified by your board core.