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Fluent Command Line Parser

A simple, strongly typed .NET C# command line parser library using a fluent easy to use interface

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A simple, strongly typed .NET C# command line parser library using a fluent easy to use interface.


See what's new in v1.4.

You can download the latest release from CodeBetter's TeamCity server

You can also install using NuGet via the command line

cmd> nuget install FluentCommandLineParser

Or use the Package Manager console in Visual Studio:

PM> Install-Package FluentCommandLineParser


See here for a side-by-side syntax comparison between other command line parsers.

Commands such as updaterecord.exe -r 10 -v="Mr. Smith" --silent can be captured using

static void Main(string[] args)
  var p = new FluentCommandLineParser();

   .Callback(record => RecordID = record)

   .Callback(value => NewValue = value)

  p.Setup<bool>('s', "silent")
   .Callback(silent => InSilentMode = silent)


Parser Option Methods

.Setup<int>('r') Setup an option using a short name,

.Setup<int>('r', "record") or short and long name.

.Required() Indicate the option is required and an error should be raised if it is not provided.

.Callback(val => Value = val) Provide a delegate to call after the option has been parsed

.SetDefault(int.MaxValue) Define a default value if the option was not specified in the args

.WithDescription("Execute operation in silent mode without feedback") Specify a help description for the option

Parsing Using the Generic Fluent Command Line Parser

Instead of assigning parsed values to variables you can use the generic Fluent Command Line Parser to automatically create a defined object type and setup individual Options for each strongly-typed property. Because the generic parser is simply a wrapper around the standard fluent parser you can still use the Fluent Command Line Parser Api to define the behaviour for each Option.

The generic Fluent Command Line Parser can build a type and populate the properties with parsed values such as in the following example:

public class ApplicationArguments
   public int RecordId { get; set; }
   public bool Silent { get; set; }
   public string NewValue { get; set; }

static void Main(string[] args)
   // create a generic parser for the ApplicationArguments type
   var p = new FluentCommandLineParser<ApplicationArguments>();

   // specify which property the value will be assigned too.
   p.Setup(arg => arg.RecordId)
    .As('r', "record") // define the short and long option name
    .Required(); // using the standard fluent Api to declare this Option as required.

   p.Setup(arg => arg.NewValue)
    .As('v', "value")

   p.Setup(arg => arg.Silent)
    .As('s', "silent")
    .SetDefault(false); // use the standard fluent Api to define a default value if non is specified in the arguments

   var result = p.Parse(args);

   if(result.HasErrors == false)
      // use the instantiated ApplicationArguments object from the Object property on the parser.

Parsing To Collections

Many arguments can be collected as part of a list. Types supported are string, int, double, bool and Enum

For example arguments such as

--filenames C:\file1.txt C:\file2.txt "C:\other file.txt"

can be automatically parsed to a List<string> using

static void Main(string[] args)
   var p = new FluentCommandLineParser();

   var filenames = new List<string>();

   p.Setup<List<string>>('f', "filenames")
    .Callback(items => filenames = items);


   Console.WriteLine("Input file names:");

   foreach (var filename in filenames)


Input file names
C:\other file.txt

Enum support

Since v1.2.3 enum types are now supported.

enum Direction
    North = 1,
    East = 2,
    South = 4,
    West = 8,
 .Callback(d => direction = d);

To specify 'East' direction either the text can be provided or the enum integer.

dosomething.exe --direction East
dosomething.exe --direction 2

You can also collect multiple Enum values into a List

List<Direction> direction;

p.Setup<List<Direction>>('d', "direction")
 .Callback(d => direction = d);

For example, specifiying 'South' and 'East' values

dosomething.exe --direction South East
dosomething.exe --direction 4 2

Since v1.4 Enum Flags are also supported

Direction direction;

 .Callback(d => direction = d);



And the generic FluentCommandLineParser (previously known as FluentCommandLineBuilder) also supports enums.

public class Args
   public Direction Direction { get;set; }
   public List<Direction> Directions { get;set; }
var p = new FluentCommandLineParser<Args>();

p.Setup(args => args.Direction)
 .As('d', "direction");

p.Setup(args => args.Directions)

Supported Syntax

[-|--|/][switch_name][=|:| ][value]

Supports boolean names

example.exe -s  // enable
example.exe -s- // disabled
example.exe -s+ // enable

Supports combined (grouped) options

example.exe -xyz  // enable option x, y and z
example.exe -xyz- // disable option x, y and z
example.exe -xyz+ // enable option x, y and z


Fclp is in the early stages of development. Please feel free to provide any feedback on feature support or the Api itself.

If you would like to contribute, you may do so to the develop branch.