/warnaserror[+ | -]
The /warnaserror+ option treats all warnings as errors. Any messages that would ordinarily be reported as warnings are instead reported as errors, and the build process is halted (no output files are built).
By default, /warnaserror- is in effect, which causes warnings to not prevent the generation of an output file. /warnaserror, which is the same as /warnaserror+, causes warnings to be treated as errors.
Use /warn to specify the level of warnings that you want the compiler to display.
Compile in.cs
and have the compiler display no warnings:
csc /warnaserror in.cs