Guard clause library for DotNet written in C#

This package contains a custom class named Guard that implements the guard clause for DotNet applications.

Current guard operations

Below you will find a list with the guard operations supported grouped by data type.

Strings

• IsEmpty
• NotEmpty
• Length
• Contains
• NotContains
• StarsWith
• NotStartsWith
• EndsWith
• NotEndsWith

IComparable

Now all types that implements the IComparable interface can be used in the following operations

• InRange
• IsLower
• IsLowerOrEquals
• IsGreater
• IsGreaterOrEquals
• NotContains

Equatable

Now all types that implements the IEquatable interface can be used in the following operations

• IsEquals
• NotEquals

Collections

Types that implements the ICollection interface can be used in the following operations

• Contains
• NotContains
• IsEmpty
• NotEmpty

Boolean

Perform guard operations for bool types

• IsTrue
• IsFalse

Regular Expressions

Given a regular expression, perform guard clause in a string

• Match
• NotMatch

Example

public class PaymentEntity
{
    public record CreditCard
    {
        public string CVV { get; set; }
        public string CardNumber { get; set; }
        public string OwnerName { get; set; }
    }

    public CreditCard Card { get; set; }
    public List<object> Cart { get; private set; }

    public PaymentEntity() 
    {
        Card = new CreditCard();
        Cart = new List<object>();
    }

    public void SetCreditCard(string owner, string number, string cvv)
    {
        Card.OwnerName = owner;
        Card.CardNumber = number;
        Card.CVV = cvv;
    }

    public void AddItem(string name)
    {
        Cart.Add(name);
    }
}

And now, let's apply the guard clause to check that parameters are in the expected format.

using Fitomad.Guard;

...

public void Buy(PaymentEntity entity)
{
    Guard.IsNotNull(entity); // Parameter is not null
    Guard.IsNotNull(entity.Card); // Credit card parameter is not null
    Guard.NotEmpty(entity.Cart); // There are items in the cart

    Guard.Length(entity.Card.CVV, stringLength: 3); // Card cvv number is 3 characters length
    Guard.Match(entity.Card.CVV, regularExpression: @"\d{3}"); // Card cvv is only digits
    Guard.Match(entity.Card.CardNumber, regulaExpression: @"\d{4}\s*\d{4}\s*\d{4}\s*\d{4}"); // Card number format
    Guard.NotEmpty(entity.Card.OwnerName); // Card owner name is filled

    ...
}

Execute custom code if guard clause fails

Fitomad.Guard package allow developers to execute custom code in case a guard clause fails

Guard.NotEmpty(entity.Cart, perform: () => 
{
    Trace.WriteLine("The customer part is empty. No products found");
});

In the example above, if guard clause fails the Trace.WriteLine code is executed before an exception will be throwed.

Custom Exceptions

You can also throw your own exceptions in case the guard clause fails.

Guard.NotEmpty(entity.Cart, perform: () => 
{
    throw new BuyUseCaseException("The customer part is empty. No products found");
});