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/warnaserror (Treat Warnings as Errors) (C# Compiler Options) 

The /warnaserror+ option treats all warnings as errors

/warnaserror[<U>+</U> | -][:warning-list]

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.

Optionally, if you want only a few specific warnings to be treated as errors, you may specify a comma-separated list of warning numbers to treat as errors.

Use /warn to specify the level of warnings that you want the compiler to display. Use /nowarn to disable certain warnings.

To set this compiler option in the Visual Studio development environment

  1. Open the project's Properties page. For details, see How to: Set Project Properties (C#, J#).

  2. Click the Build property page.

  3. Modify the Treat Warnings As Errors property.

    To set this compiler option programmatically, see TreatWarningsAsErrors.

Compile in.cs and have the compiler display no warnings:

csc /warnaserror in.cs
csc /warnaserror:642,649,652 in.cs