Raffinert.Spec 1.5.2

Raffinert.Spec

Raffinert.Spec is a rethinking of libraries such as:

• NSpecifications.
• SpecificationPattern.
• Ardalis.Specification.
• LINQKit.
• SpeciVacation.

Why Another Specification Library?

1. Cleaner IDE: Raffinert.Spec doesn't add any extension methods to common classes like object or Expression<Func<TEntity, bool>>. This means you won't see a lot of extra options in your IntelliSense.

2. Simple Design: All the 'magic' is incapsulated inside the Spec<T> and then can be explicitly or implicitly converted to Expression<Func<TEntity, bool>>. No Includes, Paginations and other extra features.

3. Flexible Use: It supports a mixed approach by allowing the use of separate specification classes as well as inline specifications. This makes it easy to combine expressions, including nested items, with no fragile code.

Usage

Full examples see in Integration Tests

Defining a Specification

You can define specifications either inline or create custom specification classes. Below is an example of a custom specification for filtering products by name:

using Raffinert.Spec;
using System.Linq.Expressions;

public class ProductNameSpec : Spec<Product>
{
    private readonly string _name;

    public ProductNameSpec(string name)
    {
        _name = name;
    }

    public override Expression<Func<Product, bool>> GetExpression()
    {
        return product => product.Name == _name;
    }
}

Composing Specifications

You can combine specifications using logical operators (AND, OR, NOT) with method chaining or operator overloads. Here are some examples using a test context:

Example: Filtering Products

// Arrange
var appleSpec = new ProductNameSpec("Apple");
var bananaSpec = Spec<Product>.Create(p => p.Name == "Banana");
var bananaOrAppleSpec = bananaSpec || appleSpec; // OR specification
var notBananaAndNotAppleSpec = !bananaOrAppleSpec; // NOT specification

// Act
var productsQuery = _context.Products.Where(notBananaAndNotAppleSpec);
var filteredProducts = await productsQuery.ToArrayAsync();

// Assert
Assert.Equivalent(new[] 
{
    new Product { Id = 3, Name = "Cherry", Price = 8.0m }
}, filteredProducts);

Filtering with Methods

You can also define specifications using methods:

// Arrange
var bananaSpec = Spec<Product>.Create(p => p.Name == "Banana");
var bananaOrAppleSpec = bananaSpec.Or(p => p.Name == "Apple"); // OR specification
var notBananaAndNotAppleSpec = !bananaOrAppleSpec; // NOT specification

// Act
var filteredProducts = _context.ProductArray.Where(notBananaAndNotAppleSpec).ToArray();

// Assert
Assert.Equivalent(new[] 
{
    new Product { Id = 3, Name = "Cherry", Price = 8.0m }
}, filteredProducts);

Complex Specification Composition

You can also compose specifications across multiple entities, as shown in the following example:

// Arrange
var bananaStringSpec = Spec<string>.Create(n => n == "Banana");
var categoryWithBanana = Spec<Category>.Create(c => c.Products.Any(p => bananaStringSpec.IsSatisfiedBy(p.Name)));

var bananaSpec1 = Spec<Product>.Create(p => p.Name == "Banana");
var categoryWithBananaProductMethodGroup = Spec<Category>.Create(c => c.Products.Any(bananaSpec1.IsSatisfiedBy));

var appleSpec = new ProductNameSpec("Apple");
var categoryWithAppleProduct = Spec<Category>.Create(c => c.Products.Any(p => appleSpec.IsSatisfiedBy(p)));

// Act1
var catQuery1 = _context.Categories.Where(categoryWithBanana);
var filteredCategories1 = await catQuery1.ToArrayAsync();

// Act2
var catQuery2 = _context.Categories.Where(categoryWithBananaProductMethodGroup);
var filteredCategories2 = await catQuery2.ToArrayAsync();

// Act3
var catQuery3 = _context.Categories.Where(categoryWithAppleProduct);
var filteredCategories3 = await catQuery3.ToArrayAsync();

// Assert
Category[] expectedCategories =
[
    new Category
    {
        Id = 1,
        Name = "Fruit"
    }
];

Assert.Equivalent(expectedCategories, filteredCategories1);
Assert.Equivalent(expectedCategories, filteredCategories2);
Assert.Equivalent(expectedCategories, filteredCategories3);

Evaluating Specifications

You can evaluate if an object satisfies a specification using the IsSatisfiedBy method:

// Example usage
var isSatisfied = bananaSpec.IsSatisfiedBy(new Product { Name = "Banana" }); // true

Debugging

The Spec<T> class includes built-in debugging support with a custom debugger display, giving developers an immediate view of the underlying expression while debugging.