C# CommandLineParser --help printing then stopping

Question

I'm building a C# console app which uses CommandLineParser to get some arguments from cmd.

The library already comes by default with the --help (or help verb) to display help information about each parameter accepted.

Now when I run the --help command I do get the help screen, but then the program continues, but it breaks, as the other default parameters are not set.

Code looks like this:

class Options
{
    [Option('f', "force", Required = false, Default = false,
        HelpText = "Force ....")]
    public bool Force { get; set; }

    [Option('v', "version", Required = false, Default = "",
        HelpText =
            "....")]
    public string Version { get; set; }

    [Option('s', "silent", Required = false, Default = false, HelpText = "Disables output ...")]
    public bool Output { get; set; }

    [Option('p', "path", Required = false, Default = "../some/dir/",
        HelpText =
            "Specifies the path ...")]
    public string StartPath { get; set; }
}

Then in the program:

static int Main(string[] args)
{

    try
    {

        var opts = new Options();

        Parser.Default.ParseArguments<Options>(args).WithParsed(parsed => opts = parsed);

        string version = opts.Version;

        PATCH_LOCATION = opts.StartPath;

        ....

So I get the help screen, and then the program keeps running (breaks as opts.StarPath is not set, neither is any of the other defaults).

Any idea how to "exit" the program when the "help" command is received?

NOTE: CommandLineParser also throws a help screen if an unknown parameter is used, which should also exit the program.

score 24 · Accepted Answer · answered Jul 31 '18 at 16:57

24

You should check the ParseResult returned by WithParsed:

var result = Parser.Default
    .ParseArguments<Options>(args)
    .WithParsed(parsed => opts = parsed);
if (result.Tag == ParserResultType.NotParsed)
{
    // Help text requested, or parsing failed. Exit.
    return 1;
}

(I believe that requesting help is equivalent to failed parsing. Definitely worth checking.)

answered Jul 31 '18 at 16:57

Jon Skeet

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Awesome! Thanks, it works. Noticed that just using the verb, it doesn't work. Example `app.exe help` runs the program as if there where no parameters. – Fede E. Jul 31 '18 at 17:02
@FedeE.: Do you mean `app.exe help` returns as if it's parsed correctly without displaying help text, but `app.exe --help` shows the help and then returns as "not parsed"? What happens with something else, like `app.exe foo`? – Jon Skeet Jul 31 '18 at 17:05
Correct! Using any word, like `app.exe aaabbb` runs the program as if there was no arguments (no errors thrown either). – Fede E. Jul 31 '18 at 18:27
@FedeE.: Hmm... I wonder whether actually it's putting that in an option somewhere. I'd need to check a complete example to see for sure. – Jon Skeet Jul 31 '18 at 18:33
I really don't know. I saw that in the documentation: `Supports --help, --version, version and help [verb] by default.` You have helped enough tho :). Thanks! – Fede E. Jul 31 '18 at 18:40

C# CommandLineParser --help printing then stopping

1 Answers1