How do I specify the exit code of a console application in .NET?

Three options:

• You can return it from Main if you declare your Main method to return int.
• You can call Environment.Exit(code).
• You can set the exit code using properties: Environment.ExitCode = -1;. This will be used if nothing else sets the return code or uses one of the other options above).

Depending on your application (console, service, web application, etc.), different methods can be used.

In addition to the answers covering the return int's... a plea for sanity. Please, please define your exit codes in an enum, with Flags if appropriate. It makes debugging and maintenance so much easier (and, as a bonus, you can easily print out the exit codes on your help screen - you do have one of those, right?).

enum ExitCode : int {
  Success = 0,
  InvalidLogin = 1,
  InvalidFilename = 2,
  UnknownError = 10
}

int Main(string[] args) {
   return (int)ExitCode.Success;
}

System.Environment.ExitCode 

See Environment.ExitCode Property.

int code = 2;
Environment.Exit( code );

Just return the appropiate code from main.

int Main(string[] args)
{
    return 0; // Or exit code of your choice
}

Use ExitCode if your main has a void return signature. Otherwise, you need to "set" it by the value you return.

From Environment.ExitCode Property:

If the Main method returns void, you can use this property to set the exit code that will be returned to the calling environment. If Main does not return void, this property is ignored. The initial value of this property is zero.

As an update to Scott Munro's answer:

• In C# 6.0 and VB.NET 14.0 (Visual Studio 2015), either Environment.ExitCode or Environment.Exit(exitCode) is required to return an non-zero code from a console application. Changing the return type of Main has no effect.
• In F# 4.0 (Visual Studio 2015), the return value of the main entry point is respected.

Use this code

Environment.Exit(0);

use 0 as the int if you don't want to return anything.

I'm doing it like this:

int exitCode = 0;
Environment.Exit(exitCode);

Or you can throw an error (personal preference):

throw new ArgumentException("Code 0, Environment Exit");

I've choose ArgumentException, but you can type other. It will work fine.

Just another way:

public static class ApplicationExitCodes
{
    public static readonly int Failure = 1;
    public static readonly int Success = 0;
}