Adding and Deleting Source Files

As your project becomes bigger, you should split it into individual source files to keep a clear structure.

Having separate source files also reduces compilation time, at least if you decide to use .CPP files instead of .INO files, see later.
The resulting program will be identical, independent of having one or multiple source files. It's just a matter of organization of your sources.

Adding a new source file

In the menu, click vMicro > Add Code:

1	Add Empty .ino	Adds a new, empty .ino file to your project
2	Add Empty Arduino .cpp and Header	Adds an empty .cpp file and a corresponding, empty .h file
3	Add Empty Arduino .c and Header	Adds an empty .c file and a corresponding, empty .h file
4	Add New Arduino Class and Header	Adds a .cpp and a .h file containing a skeleton c++ class
5	Add Local Board.txt	Adds a board.txt file to the project. The board.txt file has the same purpose and structure as the Arduino BOARDS.TXT and PLATFORM.TXT files, and can be used to override settings from BOARDS.TXT and PLATFORM.TXT for this project. The resulting board and platform settings are those from BOARDS.TXT and PLATFORM.TXT, superseded by the settings from the project specific board.txt file.
5	Add Custom GDB Debugger (Advanced)	Adds a board.txt file to the project, along with a debugger_launch.json file, allowing fine tuning / configuration of the hardware debugger. This allows custom configuration of the debugger as explained further here.

After clicking the menu item, a new and empty .INO, .C or a .CPP file are added to your project. You will be prompted for a filename. Enter the filename without the extension.

All three file types are used to write source code.

What is the difference between these file types?

Arduino .INO files are the Arduino standard. When compiling, Visual Micro treats all .INO files as they were one file. That's why you don't have to deal with include files (.H extension) as long as you are using .INO files only.
.C files are used to write code that is written in the C language. Unless you have special reasons, you should not use .C files, because the C language has no obvious advantages over the language Arduino uses normally and can cause compatibility issues.
Mixing C and C++ in one project requires profound knowledge of the languages and the compiler.
.CPP files are used to write code that is written in the C++ language. This is the same language the .INO files use. Along with the .CPP file, Visual studio also creates a matching .H file.

Which file type shall I use?

This article tells you more about the difference between .INO files and .CPP files and helps you in choosing the right file format.

Adding Existing Source Files

Use the Project > Add Existing Item menu command to add existing source files. These files can be located anywhere on your disk, not only in your project folder.

If you want to remove a file from your project, click on it in the solution explorer and press [Del]. If you do so, a box appears that lets you choose between removal and deletion.

Removing a file means that it is no longer part of your project, but it remains on your disk. You can add it again later by using Project > Add Existing Item.

Deleting a file will remove it from the project and delete the file from your hard drive as well.

Note:

Some of the methods shown above make your project incompatible with the original Arduino IDE.
If you plan to use such a project again in the original IDE, Follow these steps to make your project compatible again.

Adding Source Files from Other Projects - Sharing Source Files Among Projects

If you have multiple projects and want to share certain source files among them, then Visual Micro offers a convenient way for it.

Open a Windows Explorer window and navigate to the project where the source files are stored, that you want to share.
Navigate to the project that shall share these files with the first project
Right mouse click, and choose "Create Shortcut", this creates shortcuts of these files in this project folder
Remove the "Shortcut" from the file names of the shortcuts, so that e.g. "myfile - Shortcut.cpp" becomes "myfile.cpp"
Add the shortcuts to your project in the same way as you would add "real files", as described above