How to dynamically combine conditions?

Question

This question is an improvement on the answer to the question. How to apply several filter conditions (simultaneously) in the list?

In the above question, we have a method that the operator applied ANDto all specifications. This is achieved using the LINQ Allspecification operator .

    public static List<Product> GetProductsUisngAndFilters(List<Product> productList, List<Specification<Product>> productSpecifications)
    {
        return productList.Where(p => productSpecifications.All(ps => ps.IsSatisfiedBy(p))).ToList();
    }

We need to create a new method (GetProductsUisngDynamicFilters) that is able to fulfill specifications AND, ORand NOT(and their combination). Any idea how we can solve this?

Filter methods

public static class ProductFilterHelper
{
     public static List<Product> GetProductsUisngAndFilters(List<Product> productList, List<Specification<Product>> productSpecifications)
    {
        return productList.Where(p => productSpecifications.All(ps => ps.IsSatisfiedBy(p))).ToList();
    }
}

Client

class Program
{

    static void Main(string[] args)
    {

        List<Product> list = new List<Product>();

        Product p1 = new Product(false, 99);
        Product p2 = new Product(true, 99);
        Product p3 = new Product(true, 101);
        Product p4 = new Product(true, 110);
        Product p5 = new Product(false, 110);

        list.Add(p1);
        list.Add(p2);
        list.Add(p3);
        list.Add(p4);
        list.Add(p5);

        double priceLimit = 100;

        List<Specification<Product>> specifications = new List<Specification<Product>>();
        specifications.Add(new OnSaleSpecificationForProduct());
        specifications.Add(new PriceGreaterThanSpecificationForProduct(priceLimit));
        specifications.Add(new PriceGreaterThan105());

        List<Product> selectedList = ProductFilterHelper.GetProductsBasedOnInputFilters(list, specifications);

        Console.ReadKey();
    }

}

Abstract characteristics

public abstract class Specification<T>
{
    public abstract bool IsSatisfiedBy(T obj);

    public AndSpecification<T> And(Specification<T> specification)
    {
        return new AndSpecification<T>(this, specification);
    }

    public OrSpecification<T> Or(Specification<T> specification)
    {
        return new OrSpecification<T>(this, specification);
    }

    public NotSpecification<T> Not(Specification<T> specification)
    {
        return new NotSpecification<T>(this, specification);
    }
}

public abstract class CompositeSpecification<T> : Specification<T>
{
    protected readonly Specification<T> _leftSide;
    protected readonly Specification<T> _rightSide;

    public CompositeSpecification(Specification<T> leftSide, Specification<T> rightSide)
    {
        _leftSide = leftSide;
        _rightSide = rightSide;
    }
}

General characteristics

public class AndSpecification<T> : CompositeSpecification<T>
{
    public AndSpecification(Specification<T> leftSide, Specification<T> rightSide)
        : base(leftSide, rightSide)
    {

    }

    public override bool IsSatisfiedBy(T obj)
    {
        return _leftSide.IsSatisfiedBy(obj) && _rightSide.IsSatisfiedBy(obj);
    }
}

public class OrSpecification<T> : CompositeSpecification<T>
{
    public OrSpecification(Specification<T> leftSide, Specification<T> rightSide)
        : base(leftSide, rightSide)
    {
    }

    public override bool IsSatisfiedBy(T obj)
    {
        return _leftSide.IsSatisfiedBy(obj) || _rightSide.IsSatisfiedBy(obj);
    }
}

public class NotSpecification<T> : CompositeSpecification<T>
{
    public NotSpecification(Specification<T> leftSide, Specification<T> rightSide)
        : base(leftSide, rightSide)
    {
    }

    public override bool IsSatisfiedBy(T obj)
    {
        return _leftSide.IsSatisfiedBy(obj) && !_rightSide.IsSatisfiedBy(obj);
    }
}

Product Specifications

public class OnSaleSpecificationForProduct : Specification<Product>
{
    public override bool IsSatisfiedBy(Product product)
    {
        return product.IsOnSale;
    }
}

public class PriceGreaterThanSpecificationForProduct : Specification<Product>
{
    private readonly double _price;
    public PriceGreaterThanSpecificationForProduct(double price)
    {
        _price = price;
    }

    public override bool IsSatisfiedBy(Product product)
    {
        return product.Price > _price;
    }
}

public class PriceGreaterThan105 : Specification<Product>
{

    public override bool IsSatisfiedBy(Product product)
    {
        return product.Price > 105;
    }
}

Entity

public class Product
{
    private bool _isOnSale;
    private double _price = 0.0;

    public Product(bool isOnSale)
        : this(isOnSale, 0.0)
    {
        _isOnSale = isOnSale;
    }

    public Product(double price)
        : this(false, price)
    {
        _price = price;
    }

    public Product(bool isOnSale, double price)
    {
        _price = price;
        _isOnSale = isOnSale;
    }

    public bool IsOnSale
    {
        get { return _isOnSale; }
    }

    public double Price
    {
        get { return _price; }
    }
}

Answer 1

, , , . List<Specification<T>>. , Specification<T> ( CompositeSpecification<T>):

class Program
{

    static void Main(string[] args)
    {

        List<Product> list = new List<Product>();

        Product p1 = new Product(false, 99);
        Product p2 = new Product(true, 99);
        Product p3 = new Product(true, 101);
        Product p4 = new Product(true, 110);
        Product p5 = new Product(false, 110);

        list.Add(p1);
        list.Add(p2);
        list.Add(p3);
        list.Add(p4);
        list.Add(p5);

        double priceLimit = 100;

         var specification =
             new OnSaleSpecificationForProduct()
                 .And(new PriceGreaterThanSpecificationForProduct(priceLimit)
                              .Or(new PriceGreaterThan105()));

        List<Product> selectedList = ProductFilterHelper.GetProductsBasedOnInputFilters(list, specification);

        Console.ReadKey();
    }

}

:

 public static List<Product> GetProductsUisngDynamicFilters(List<Product> productList, Specification<Product> productSpecification)
    {
        return productList.Where(p => productSpecification.IsSatisfiedBy(p))
                          .ToList();
    }

Or, And Not Specification<T> . , , .