/target:module (C# Compiler Options)
This option causes the compiler to not generate an assembly manifest.
/target:module
Remarks
By default, the output file created by compiling with this option will have an extension of .netmodule.
A file that does not have an assembly manifest cannot be loaded by the .NET Framework common language runtime. However, such a file can be incorporated into the assembly manifest of an assembly by means of /addmodule.
If more than one module is created in a single compilation, internal types in one module will be available to other modules in the compilation. When code in one module references internal types in another module, then both modules must be incorporated into an assembly manifest, by means of /addmodule.
Creating a module is not supported in the Visual Studio development environment.
For information on how to set this compiler option programmatically, see OutputType.
Example
Compile in.cs, creating in.netmodule:
csc /target:module in.cs