ArgDefender

ArgDefender is a fluent argument validation library that is intuitive, fast and extensible.

Note

This project is a continuation of the archived Dawn.Guard

• ArgDefender
  • Installation
  • Introduction
  • What's Wrong with Vanilla?
    • Standard Validations
    • Design Decisions
    • Extensibility
    • Code Snippets

Installation

Using dotnet

dotnet add package ArgDefender

Using PowerShell

Install-Package ArgDefender

Introduction

Here is a sample constructor that validates its arguments without ArgDefender:

public Person(string name, int age)
{
    if (name == null)
        throw new ArgumentNullException(nameof(name), "Name cannot be null.");

    if (name.Length == 0)
        throw new ArgumentException("Name cannot be empty.", nameof(name));

    if (age < 0)
        throw new ArgumentOutOfRangeException(nameof(age), age, "Age cannot be less than zero.");

    Name = name;
    Age = age;
}

And this is how we write the same constructor with ArgDefender:

using ArgDefender;

public Person(string name, int age)
{
    Name = Guard.Argument(name, nameof(name)).NotNull().NotEmpty();
    Age = Guard.Argument(age, nameof(age)).Min(0);
}

If this looks like too much allocations to you, fear not. The arguments are read-only structs that are passed by reference. See the design decisions for details and an introduction to ArgDefender's more advanced features.

What's Wrong with Vanilla?

There is nothing wrong with writing your own checks but when you have lots of types you need to validate, the task gets very tedious, very quickly.

Let's analyze the string validation in the example without ArgDefender:

• We have an argument (name) that we need to be a non-null, non-empty string.
• We check if it's null and throw an ArgumentNullException if it is.
• We then check if it's empty and throw an ArgumentException if it is.
• We specify the same parameter name for each validation.
• We write an error message for each validation.
• ArgumentNullException accepts the parameter name as its first argument and error message as its second while it's the other way around for the ArgumentException. An inconsistency that many of us sometimes find it hard to remember.

In reality, all we need to express should be the first bullet, that we want our argument non-null and non-empty.

With ArgDefender, if you want to guard an argument against null, you just write NotNull and that's it. If the argument is passed null, you'll get an ArgumentNullException thrown with the correct parameter name and a clear error message out of the box. The standard validations have fully documented, meaningful defaults that get out of your way and let you focus on your project.

Standard Validations

Click here for a list of the validations that are included in the library.

Design Decisions

Click here for the document that explains the motives behind the ArgDefender's API design and more advanced features.

Extensibility

Click here to see how to add custom validations to ArgDefender by writing simple extension methods.

Code Snippets

Code snippets can be found in the snippets folder. Currently, only the Visual Studio is supported.