Top 20 NuGet argument Packages

Ensure.Net is a null checker library for .NET
Provides static classes for representing program contracts as preconditions in a way that's compatible with System.Diagnostics.Contracts.
Useful POSIX command line arguments parser for .Net. Hierarchical-configuration Store for app.
Cauldron.Consoles is a Cauldron.Core based parameter parser which supports grouping of parameters in execution groups. It is also supports localization and has a nice parameter table :) Breaking changes in 3.1.x - See https://github.com/Capgemini/Cauldron for more information.
Deep fork of the Seterlund.CodeGuard library. Example: Guard.That(arg1).IsNotNull().GreaterThan(100); Throws an exception if conditions are not met.
A simple guard library for validating method parameters without being a complete validation library. This library makes it easy to validate method arguments in a uniform way.
Tool for reading arguments (bool, integer, double, string) from the command line within a given schema. The tool also can easily be extended, without recompiling the whole library.
Isop is a library to help simplify and structure command line apps.
NClap is a .NET library for parsing command-line arguments and building interactive command shells. It's driven by a declarative attribute syntax, and easy to extend.
Configures Microsoft.Extensions.DependencyInjection for dependency injection
Argument validation methods, for example: this.user = Argument.NotNull("user", user). Less fancy than approaches based on lambdas/anonymous classes, but less scary performance-wise (given that argument checks are often all over the place). Annotations: C# 8 nullable reference types, ReSharper, Mic...
Simple attribute based command line parser.
The Command Line Parser Library offers to CLR applications a clean and concise API for manipulating command line arguments and related tasks. This is a fork of the original project, including most pull requests.
Tool for reading string arguments from the command line.
Base class for command line interface argument handling/building.
Tool for reading integer arguments from the command line.
Tool for reading double arguments from the command line.
Tool for reading boolean arguments from the command line.
Tool for reading double arguments from the command line.
An extension for FakeItEasy which allows for capturing arguments sent to a fake.