CommandLineParser: Required only if a value of another option is equal to?

Question

Using https://github.com/commandlineparser/commandline

I would like to set an Option as "Required" if the value parsed from another Option is equal to a particular value.

    [Option('f', "foo", Required = true, HelpText = "Name of process")]
    public string Foo{ get; set; }

    [Option('b', "bar", Required = ( Foo == "egg" ), HelpText = "Name of process")]
    public string Bar{ get; set; }

[like this](https://dotnetfiddle.net/ntrNl3) ... for common you can define base class for option — Selvin, Aug 29 '23 at 13:42

Mustafa Özçetin · Answer 1 · 2023-08-29T12:36:18.990

I don't think this is possible since .NET Attribute class has some restrictions to what kinds of arguments may be used with. You have to use a constant expression where you set the Required property. Your line

[Option('b', "bar", Required = ( Foo == "egg" ), HelpText = "Name of process")]

raises the explanatory compiler error (assuming Foo is a static property):

CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type.

CommandLineParser: Required only if a value of another option is equal to?

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