声明：以下内容来源于《大话设计模式》，学习。

策略模式：定义了算法家族，分别封装起来，让它们之间可以互相替换，此模式让算法的变化，不会影响到使用算法的客户。

商场收费策略：正常收费、打折收费、返利收费。

类图如下：

代码：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;namespace 策略模式{    /// 
    /// MainWindow.xaml 的交互逻辑    /// 
    public partial class MainWindow : Window    {        private double moneyTotal = 0d;        public MainWindow()        {            InitializeComponent();            this.cmbType.ItemsSource = Methods.MoneyMethods;            this.cmbType.SelectedIndex = 0;        }        /// 
        /// 确定        /// 
        ///         ///         private void Button_Click_1(object sender, RoutedEventArgs e)        {            CashContext cs = null;            switch (cmbType.SelectedItem.ToString())            {                case Methods.CON_NORMAL:                    cs = new CashContext(new  CasthNormal());                    break;                case Methods.CON_REBATE:                    cs = new CashContext( new CashRebate("0.8"));                    break;                case Methods.CON_RETURN:                    cs = new  CashContext( new CashReturn(300, 30));                    break;            }            double curTotalPrices = 0d;            curTotalPrices = cs.GetResult(double.Parse(txtPrice.Text.Trim()) * double.Parse(txtNum.Text.Trim()));            moneyTotal += curTotalPrices;            lstboxDetail.Items.Add("单价："+txtPrice.Text.Trim()+"数量:"+txtNum.Text.Trim()+" "+cmbType.SelectedItem.ToString()+                "合计："+curTotalPrices);            txtTotal.Text = moneyTotal.ToString();        }        /// 
        /// 重置        /// 
        ///         ///         private void Button_Click_2(object sender, RoutedEventArgs e)        {            lstboxDetail.Items.Clear();            txtPrice.Text = string.Empty;            txtNum.Text = string.Empty;            txtTotal.Text = "0";            moneyTotal = 0d;        }    }    #region 策略模式    /// 
    /// 抽象算法类    /// 
    public abstract class Strategy    {        public abstract double AcceptCash(double money);    }    /// 
    /// 正常收费子类    /// 
    public class CasthNormal : Strategy    {        public override double AcceptCash(double money)        {            return money;        }    }    /// 
    /// 打折收费子类    /// 
    public class CashRebate : Strategy    {        private double reBate = 1d;        public CashRebate(string moneyRebate)        {            reBate = double.Parse(moneyRebate);        }        public override double AcceptCash(double money)        {            return money * reBate;        }    }    /// 
    /// 返利子类    /// 
    public class CashReturn : Strategy    {        private double moneyCondition = 0d;        private double moneyReturn = 0d;        public CashReturn(double moneyConditon,double moneyReturn)        {            this.moneyCondition = moneyConditon;            this.moneyReturn = moneyReturn;        }        public override double AcceptCash(double money)        {            double moneyResult = money;            if (money >= this.moneyCondition)            {                moneyResult = money - Math.Floor(money / moneyCondition) * moneyReturn;            }            return moneyResult;        }    }    public class CashContext    {        private Strategy cs;        public CashContext(Strategy cs)        {            this.cs = cs;        }        public double GetResult(double money)        {            return cs.AcceptCash(money);        }    }    #endregion}

          
                       
                    
                         
                                              
                      
                     
                 
            
           
               
                    
                     
                     
                     
                     
                 
                
                    
                 
                
                    
         
          单价：
                     
                     
         确定        
                
                    
         
          数量：
                     
                     
         重置        
                
                    
         
          计算方式：
                     
                 
                
                            
                
                    
                         
                              
                               
                           
                      
          
           总计:
                      
          
           0