C#中的策略模式

策略模式：动态切换算法

当业务需要支持多种算法变体时，常见做法：

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if(paymentMethod == "Cash") ProcessCash();
else if(paymentMethod == "CreditCard") ProcessCreditCard();

但是这样容易出现一些问题：

  1. 新增支付方式需修改核心代码

  2. 支付逻辑与控制器耦合

  3. 难以单独测试支付算法

解决方案：策略模式

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///<策略模式>
public interface IPaymentStrategy
{ 
void ProcessPayment();
}


public class CashPaymentStrategy : IPaymentStrategy
{
    public void ProcessPayment()
    {
        Console.WriteLine("Processing cash payment");
    }
}

public class CreditCardPaymentStrategy : IPaymentStrategy
{
    public void ProcessPayment()
    {
        Console.WriteLine("Processing credit card payment");
    }
}

public class PaymentProcessor
{
    public void ProcessPayment(IPaymentStrategy paymentStrategy)
    {
        paymentStrategy.ProcessPayment();
    }
}

///<策略模式/>

设计原则

  1. 开闭原则

    • 添加新支付方式只需创建新类

    • 示例：添加PayPalStrategy无需修改处理器

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public class PayPalStrategy : IPaymentStrategy
{
    public void ProcessPayment()
    {
        Console.WriteLine("Processing PayPal payment");
    }
}

  1. 组合优于继承

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    public class PaymentProcessor
    {
        public void ProcessPayment(IPaymentStrategy paymentStrategy)
        {
            paymentStrategy.ProcessPayment();
        }
    }

  2. 单一职责原则

    • 每种策略只负责一种算法实现

    • 控制器只负责执行策略

适用场景
- 需要在运行时切换算法

- 有多个相似类仅在行为上不同

- 需要隔离复杂算法实现细节

典型应用
- 支付方式处理

- 数据压缩算法

- 导航路径计算

- 折扣计算规则

完整代码如下：

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///<策略模式>
public interface IPaymentStrategy
{ 
void ProcessPayment();
}


public class CashPaymentStrategy : IPaymentStrategy
{
    public void ProcessPayment()
    {
        Console.WriteLine("Processing cash payment");
    }
}

public class CreditCardPaymentStrategy : IPaymentStrategy
{
    public void ProcessPayment()
    {
        Console.WriteLine("Processing credit card payment");
    }
}

public class PaymentProcessor
{
    public void ProcessPayment(IPaymentStrategy paymentStrategy)
    {
        paymentStrategy.ProcessPayment();
    }
}

///<策略模式/>
public class Program
{
    public static void Main(string[] args)
    {
        ///<策略模式>
        Console.WriteLine();
        Console.WriteLine("策略模式:");
        PaymentProcessor paymentProcessor = new PaymentProcessor();
        paymentProcessor.ProcessPayment(new CashPaymentStrategy());
        paymentProcessor.ProcessPayment(new CreditCardPaymentStrategy());
        ///<策略模式/>
     }
}