light-traveller/LightTraveller.Guards

A throw helper (guard) library for .NET

LightTraveller.Guards

This throw helper (guard) library allows you to skip typing boilerplate code to guard against unacceptable arguments passed to a method. This helps to produce a cleaner and more readable code

---

Example: Checking for null

The following method

using LightTraveller.Guards;

public class TicketService
{
    private readonly TicketRepository _repository;
    private readonly UserService _userService;
    private readonly TicketValidator _validator;
    

    public TicketService(TicketRepository repository, UserService userService, TicketValidator validator)
    {
        if (repository is null)
            throw new ArgumentNullException(nameof(repository));

        if (userService is null)
            throw new ArgumentNullException(nameof(userService));

        if (validator is null)
            throw new ArgumentNullException(nameof(validator));
        
        _repository = repository;
        _userService = userService;
        _validator = validator; 
    }
}

can be rewritten as

using LightTraveller.Guards;

public class TicketService
{
    private readonly TicketRepository _repository;
    private readonly UserService _userService;
    private readonly TicketValidator _validator;
    

    public TicketService(TicketRepository repository, UserService userService, TicketValidator validator)
    {
        _repository = Guard.Null(repository);        
        _userService = Guard.Null(userService);

        // An overload accepting a custom exception message
        _validator = Guard.Null(validator, "Make sure the passed argument is not null.");
    }
}

Notice

As you can see in the example above, when using Guards library, you do not need to pass the name of the arguments, e.g., nameof(repository) or "repository", to the guard methods to be used for throwing exceptions. This is taken care of by using [CallerArgumentExpression] attribute in the the methods of the Guard class.

---

Installation

You can add the Nuget package of the LightTraveller.Guards by running the following command in the .NET CLI

dotnet add package LightTraveller.Guards --version <VERSION NUMBER>

For more information please go to the nuget.org page of this library.

How to Use

1. Add this to the using statements in your code: using LightTraveller.Guards;
2. Simply call static methods of the Guard class by passing the argument to be checked to that method. Each method returns the instance passed to it if it passes the check; otherwise, throws an exception.

For a code sample, please look at the above example.

Available Methods

1. Guard.Null throws if the generic input is null.
2. Guard.Empty throws if the string input is null, an empty string or consists only of white-space characters.
3. Gurad.NullOrEmpty throws if the IEnumerable<T> input is null, or an empty collection.
4. Guard.Zero throws if the input is zero.
5. Guard.Negative throws if the input is negative.
6. Guard.ZeroOrNegative throws if the input is zero or negative.
7. Guard.Positive throws if the input is positive.
8. Guard.ZeroOrPositive throws if the input is zero or positive.
9. Guard.OutOfRange throws if the generic IComparable<T> input is out of the specified range.
10. Guard.InvalidEnumValue throws if the input cannot be cast to a member of the specified enumeration.
11. Guard.ZeroPointer throws if the input is IntPtr.Zero.