CODESAMPLE

Policy - C#

Policy C_sharp

The Policy pattern allows you to encapsulate a changeable algorithm or set of rules into a separate object. This promotes flexibility as you can swap out different policies at runtime without modifying the core logic that uses the policy. This example demonstrates a simple pricing policy. The PricingService class depends on an IPricingPolicy interface. Different concrete policies (e.g., StandardPricingPolicy, DiscountedPricingPolicy) implement the pricing logic. The client can inject the desired policy, enabling dynamic pricing strategies. This approach aligns with C#’s dependency injection principles and interface-based programming, making the code testable and maintainable.

// IPricingPolicy.cs
public interface IPricingPolicy
{
    decimal CalculatePrice(decimal originalPrice, int quantity);
}

// StandardPricingPolicy.cs
public class StandardPricingPolicy : IPricingPolicy
{
    public decimal CalculatePrice(decimal originalPrice, int quantity)
    {
        return originalPrice * quantity;
    }
}

// DiscountedPricingPolicy.cs
public class DiscountedPricingPolicy : IPricingPolicy
{
    private readonly decimal _discountPercentage;

    public DiscountedPricingPolicy(decimal discountPercentage)
    {
        _discountPercentage = discountPercentage;
    }

    public decimal CalculatePrice(decimal originalPrice, int quantity)
    {
        decimal discountFactor = 1 - _discountPercentage;
        return (originalPrice * quantity) * discountFactor;
    }
}

// PricingService.cs
public class PricingService
{
    private readonly IPricingPolicy _pricingPolicy;

    public PricingService(IPricingPolicy pricingPolicy)
    {
        _pricingPolicy = pricingPolicy;
    }

    public decimal GetPrice(decimal originalPrice, int quantity)
    {
        return _pricingPolicy.CalculatePrice(originalPrice, quantity);
    }
}

// Example Usage (Program.cs)
public class Program
{
    public static void Main(string[] args)
    {
        // Use standard pricing
        var standardPolicy = new StandardPricingPolicy();
        var pricingServiceStandard = new PricingService(standardPolicy);
        decimal price1 = pricingServiceStandard.GetPrice(10, 5);
        Console.WriteLine($"Standard Price: {price1}");

        // Use discounted pricing
        var discountPolicy = new DiscountedPricingPolicy(0.1m); // 10% discount
        var pricingServiceDiscount = new PricingService(discountPolicy);
        decimal price2 = pricingServiceDiscount.GetPrice(10, 5);
        Console.WriteLine($"Discounted Price: {price2}");
    }
}