/warn (Specify Warning Level) (C# Compiler Options)

option

The warning level you want displayed for the compilation: Lower numbers show only high severity warnings; higher numbers show more warnings. Valid values are 0-4:

Warning level	Meaning
0	Turns off emission of all warning messages.
1	Displays severe warning messages.
2	Displays level 1 warnings plus certain, less-severe warnings, such as warnings about hiding class members.
3	Displays level 2 warnings plus certain, less-severe warnings, such as warnings about expressions that always evaluate to true or false.
4 (the default)	Displays all level 3 warnings plus informational warnings.

To get information about an error or warning, you can look up the error code in the Help Index. For other ways to get information about an error or warning, see How to: Locate Help for Compiler Errors.

Use /warnaserror to treat all warnings as errors. Use /nowarn to disable certain warnings.

/w is the short form of /warn.

To set this compiler option in the Visual Studio development environment

For information on how to set this compiler option programmatically, see WarningLevel.

Compile in.cs and have the compiler only display level 1 warnings:

csc /warn:1 in.cs

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