# -nostdlib (C# Compiler Options)

-nostdlib prevents the import of mscorlib.dll, which defines the entire System namespace.

## Syntax

-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 is imported into your program (same as specifying -nostdlib-). Specifying -nostdlib is the same as specifying -nostdlib+.

### To set this compiler option in Visual Studio

Note

The following instructions apply to Visual Studio 2015 (and earlier versions) only. The Do not reference mscorlib.dll build property doesn't exist in Visual Studio 2017.

1. Open the Properties page for the project.

2. Click the Build properties page.