Best way to parse command line arguments in C#?


When building console applications that take parameters, you can use the arguments passed to Main(string[] args).

In the past I've simply indexed/looped that array and done a few regular expressions to extract the values. However, when the commands get more complicated, the parsing can get pretty ugly.

So I'm interested in:

  • Libraries that you use
  • Patterns that you use

Assume the commands always adhere to common standards such as answered here.

5/23/2017 11:54:50 AM

Accepted Answer

I would strongly suggest using NDesk.Options (Documentation) and/or Mono.Options (same API, different namespace). An example from the documentation:

bool show_help = false;
List<string> names = new List<string> ();
int repeat = 1;

var p = new OptionSet () {
    { "n|name=", "the {NAME} of someone to greet.",
       v => names.Add (v) },
    { "r|repeat=", 
       "the number of {TIMES} to repeat the greeting.\n" + 
          "this must be an integer.",
        (int v) => repeat = v },
    { "v", "increase debug message verbosity",
       v => { if (v != null) ++verbosity; } },
    { "h|help",  "show this message and exit", 
       v => show_help = v != null },

List<string> extra;
try {
    extra = p.Parse (args);
catch (OptionException e) {
    Console.Write ("greet: ");
    Console.WriteLine (e.Message);
    Console.WriteLine ("Try `greet --help' for more information.");
6/29/2011 5:03:20 AM

I really like the Command Line Parser Library ( ). It has a very simple and elegant way of setting up parameters via attributes:

class Options
    [Option("i", "input", Required = true, HelpText = "Input file to read.")]
    public string InputFile { get; set; }

    [Option(null, "length", HelpText = "The maximum number of bytes to process.")]
    public int MaximumLenght { get; set; }

    [Option("v", null, HelpText = "Print details during execution.")]
    public bool Verbose { get; set; }

    [HelpOption(HelpText = "Display this help screen.")]
    public string GetUsage()
        var usage = new StringBuilder();
        usage.AppendLine("Quickstart Application 1.0");
        usage.AppendLine("Read user manual for usage instructions...");
        return usage.ToString();

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