/FI (Name Forced Include File)
Causes the preprocessor to process the specified header file.
This option has the same effect as specifying the file with double quotation marks in an #include directive on the first line of every source file specified on the command line, in the CL environment variable, or in a command file. If you use multiple /FI options, files are included in the order they are processed by CL.
To set this compiler option in the Visual Studio development environment
Open the project's Property Pages dialog box. For details, see How to: Open Project Property Pages.
Click the C/C++ folder.
Click the Advanced property page.
Modify the Force Includes property.
To set this compiler option programmatically