设计模式之状态机 C#范例

C#状态机设计模式是一种行为设计模式，用于管理对象基于状态的行为变化。它通过将不同状态封装为独立类，使状态转换逻辑更加清晰和可维护。

‌**核心概念：**‌

‌状态接口‌：定义所有状态共有的操作
‌具体状态类‌：实现特定状态的行为逻辑
‌上下文类‌：维护当前状态并委托状态相关操作

‌**主要优势：**‌

‌消除复杂条件判断‌：用多态替代大量的if-else或switch语句
‌开闭原则‌：易于添加新状态而不影响现有代码

‌状态转换明确‌：每个状态只允许合法的操作和转换

‌代码组织清晰‌：相关行为集中在对应的状态类中

‌**适用场景：**‌

对象行为随状态改变而显著变化
状态转换逻辑复杂且频繁修改
需要避免大量的条件分支语句

‌实现方式： ‌

通常通过定义状态接口、实现具体状态类、创建上下文类来管理状态转换，确保状态间的转换符合业务规则。

以下是代码范例：

cs 复制代码

// 订单状态接口
public interface IOrderState
{
    void Confirm(Order order);
    void Cancel(Order order);
    void Ship(Order order);
    void Deliver(Order order);
    void Complete(Order order);
}

// 待确认状态
public class PendingState : IOrderState
{
    public void Confirm(Order order)
    {
        Console.WriteLine("订单已确认");
        order.SetState(new ConfirmedState());
    }

    public void Cancel(Order order)
    {
        Console.WriteLine("订单已取消");
        order.SetState(new CancelledState());
    }

    public void Ship(Order order) => Console.WriteLine("待确认订单不能发货");
    public void Deliver(Order order) => Console.WriteLine("待确认订单不能送达");
    public void Complete(Order order) => Console.WriteLine("待确认订单不能完成");
}

// 已确认状态
public class ConfirmedState : IOrderState
{
    public void Confirm(Order order) => Console.WriteLine("订单已经是确认状态");
    
    public void Cancel(Order order)
    {
        Console.WriteLine("订单已取消");
        order.SetState(new CancelledState());
    }

    public void Ship(Order order)
    {
        Console.WriteLine("订单已发货");
        order.SetState(new ShippedState());
    }

    public void Deliver(Order order) => Console.WriteLine("已确认订单不能直接送达");
    public void Complete(Order order) => Console.WriteLine("已确认订单不能完成");
}

// 已发货状态
public class ShippedState : IOrderState
{
    public void Confirm(Order order) => Console.WriteLine("已发货订单不能重新确认");
    public void Cancel(Order order) => Console.WriteLine("已发货订单不能取消");
    
    public void Ship(Order order) => Console.WriteLine("订单已经是发货状态");
    
    public void Deliver(Order order)
    {
        Console.WriteLine("订单已送达");
        order.SetState(new DeliveredState());
    }

    public void Complete(Order order) => Console.WriteLine("已发货订单不能完成");
}

// 已送达状态
public class DeliveredState : IOrderState
{
    public void Confirm(Order order) => Console.WriteLine("已送达订单不能重新确认");
    public void Cancel(Order order) => Console.WriteLine("已送达订单不能取消");
    public void Ship(Order order) => Console.WriteLine("已送达订单不能重新发货");
    public void Deliver(Order order) => Console.WriteLine("订单已经是送达状态");
    
    public void Complete(Order order)
    {
        Console.WriteLine("订单已完成");
        order.SetState(new CompletedState());
    }
}

// 已完成状态
public class CompletedState : IOrderState
{
    public void Confirm(Order order) => Console.WriteLine("已完成订单不能重新确认");
    public void Cancel(Order order) => Console.WriteLine("已完成订单不能取消");
    public void Ship(Order order) => Console.WriteLine("已完成订单不能重新发货");
    public void Deliver(Order order) => Console.WriteLine("已完成订单不能重新送达");
    public void Complete(Order order) => Console.WriteLine("订单已经是完成状态");
}

// 已取消状态
public class CancelledState : IOrderState
{
    public void Confirm(Order order) => Console.WriteLine("已取消订单不能确认");
    public void Cancel(Order order) => Console.WriteLine("订单已经是取消状态");
    public void Ship(Order order) => Console.WriteLine("已取消订单不能发货");
    public void Deliver(Order order) => Console.WriteLine("已取消订单不能送达");
    public void Complete(Order order) => Console.WriteLine("已取消订单不能完成");
}
<code_end>
<code_start project_name=csharp_state_pattern filename=Order.cs title=订单类-状态机上下文 entrypoint=false runnable=false project_final_file=false>
// 订单类 - 状态机上下文
public class Order
{
    private IOrderState _currentState;
    public string OrderId { get; }
    public string CustomerName { get; }
    public decimal TotalAmount { get; }

    public Order(string orderId, string customerName, decimal totalAmount)
    {
        OrderId = orderId;
        CustomerName = customerName;
        TotalAmount = totalAmount;
        _currentState = new PendingState();
    }

    public void SetState(IOrderState state)
    {
        _currentState = state;
        Console.WriteLine($"订单状态已更新: {state.GetType().Name}");
    }

    public string GetCurrentState() => _currentState.GetType().Name;

    // 状态操作方法
    public void Confirm() => _currentState.Confirm(this);
    public void Cancel() => _currentState.Cancel(this);
    public void Ship() => _currentState.Ship(this);
    public void Deliver() => _currentState.Deliver(this);
    public void Complete() => _currentState.Complete(this);

    public void DisplayStatus()
    {
        Console.WriteLine($"订单 {OrderId} - 客户: {CustomerName} - 金额: {TotalAmount:C} - 当前状态: {GetCurrentState()}");
    }
}
<code_end>
<code_start project_name=csharp_state_pattern filename=StateTransition.cs title=状态转换规则管理器 entrypoint=false runnable=false project_final_file=false>
using System.Collections.Generic;

// 状态转换规则
public class StateTransition
{
    public string FromState { get; }
    public string Action { get; }
    
    public StateTransition(string fromState, string action)
    {
        FromState = fromState;
        Action = action;
    }

    public override bool Equals(object obj)
    {
        return obj is StateTransition transition &&
               FromState == transition.FromState &&
               Action == transition.Action;
    }

    public override int GetHashCode()
    {
        return System.HashCode.Combine(FromState, Action);
    }
}

// 状态机配置
public class StateMachineConfiguration
{
    private readonly Dictionary<StateTransition, string> _transitions;

    public StateMachineConfiguration()
    {
        _transitions = new Dictionary<StateTransition, string>
        {
            // 从待确认状态可以转换到已确认或已取消
            { new StateTransition("PendingState", "Confirm"), "ConfirmedState" },
            { new StateTransition("PendingState", "Cancel"), "CancelledState" },
            
            // 从已确认状态可以转换到已发货或已取消
            { new StateTransition("ConfirmedState", "Ship"), "ShippedState" },
            { new StateTransition("ConfirmedState", "Cancel"), "CancelledState" },
            
            // 从已发货状态只能转换到已送达
            { new StateTransition("ShippedState", "Deliver"), "DeliveredState" },
            
            // 从已送达状态只能转换到已完成
            { new StateTransition("DeliveredState", "Complete"), "CompletedState" }
        };
    }

    public bool IsValidTransition(string fromState, string action, out string toState)
    {
        var transition = new StateTransition(fromState, action);
        return _transitions.TryGetValue(transition, out toState);
    }

    public IEnumerable<string> GetAvailableActions(string currentState)
    {
        var actions = new List<string>();
        
        foreach (var transition in _transitions)
        {
            if (transition.Key.FromState == currentState)
            {
                actions.Add(transition.Key.Action);
            }
        }
        
        return actions;
    }
}
<code_end>
<code_start project_name=csharp_state_pattern filename=Program.cs title=状态机演示程序主入口 entrypoint=true runnable=true project_final_file=true>
using System;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("=== C# 状态机设计模式演示 ===\n");

        // 创建订单
        var order = new Order("ORD001", "张三", 299.99m);
        order.DisplayStatus();

        // 演示正常状态流转
        Console.WriteLine("\n--- 正常状态流转演示 ---");
        order.Confirm();
        order.Ship();
        order.Deliver();
        order.Complete();
        order.DisplayStatus();

        // 演示无效操作
        Console.WriteLine("\n--- 无效操作演示 ---");
        order.Confirm();  // 已完成订单不能重新确认

        // 创建新订单演示取消流程
        Console.WriteLine("\n--- 取消流程演示 ---");
        var order2 = new Order("ORD002", "李四", 159.50m);
        order2.DisplayStatus();
        order2.Cancel();
        order2.DisplayStatus();
        order2.Ship();  // 已取消订单不能发货

        // 状态机配置演示
        Console.WriteLine("\n--- 状态机配置演示 ---");
        var config = new StateMachineConfiguration();
        
        var currentState = "PendingState";
        Console.WriteLine($"当前状态: {currentState}");
        Console.WriteLine("可用操作: " + string.Join(", ", config.GetAvailableActions(currentState)));

        // 验证转换规则
        if (config.IsValidTransition("PendingState", "Confirm", out var toState))
        {
            Console.WriteLine($"有效转换: PendingState -> Confirm -> {toState}");
        }

        if (!config.IsValidTransition("CompletedState", "Cancel", out _))
        {
            Console.WriteLine("无效转换: CompletedState -> Cancel");
        }

        Console.WriteLine("\n演示结束！");
    }
}

设计模式之 状态机 C#范例

设计模式之状态机 C#范例