Add FluentValidation to validate the parsed options

Setup

You need to add the following package to your project that will allow to use FluentValidation with CommandLineParser

PM> Install-Package MatthiWare.CommandLineParser.Extensions.FluentValidations

Example

using FluentValidation;
using MatthiWare.CommandLine.Extensions.FluentValidations;

static void Main(string[] args)
{
    var parser = new CommandLineParser<ProgramOptions>();

    // Plugin the FluentValidation library
    parser.UseFluentValidations(configurator
        => configurator.AddValidator<ProgramOptions, ProgramOptionValidator>());

    // Rest of the configuration..
}

// The options
public class ProgramOptions
{
    [Required, Name("user", "username"), Description("Login user")]
    public string Username { get; set; }

    [Required, Name("pw", "password"), Description("Password for the user")]
    public string Password { get; set; }

    [Required, Name("p", "port"), Description("port for the server"), DefaultValue(3333)]
    public int Port { get; set; }
}

// The FluentValidation implementation
public class ProgramOptionValidator : AbstractValidator<ProgramOptions>
{
    public ProgramOptionValidator()
    {
        RuleFor(o => o.Password).MinimumLength(5);
        RuleFor(o => o.Username).MinimumLength(5);
        RuleFor(o => o.Port).InclusiveBetween(1000, 30000);
    }
}