/nostdlib prevents the import of mscorlib.dll, which defines the entire System namespace.
/nostdlib[+ | -]
Remarks
Use this option if you want to define or create your own System namespace and objects.
If you do not specify /nostdlib, mscorlib.dll will be imported into your program (same as specifying /nostdlib-). Specifying /nostdlib is the same as specifying /nostdlib+.
To set this compiler option in the Visual Studio development environment
- Open the Properties page for the project. 
- Click the Build properties page. 
- Click the Advanced button. 
- Modify the Do not reference mscorlib.dll property. 
For information on how to set this compiler option programmatically, see NoStdLib.
See Also
Tasks
How to: Modify Project Properties and Configuration Settings