/// 
    /// 现金收费抽象类    /// 
    public abstract class CashSuper    {        public abstract double acceptCash(double money);    }

/// 
    /// 正常收费子类    /// 
    public class CashNormal : CashSuper     {        public override double acceptCash(double money)        {            return money;        }    }

/// 
    /// 打折收费子类    /// 
    public class CashRebate : CashSuper     {        private double moneyRebate = 1d;        public CashRebate(string moneyRebate)         {            this.moneyRebate = double.Parse(moneyRebate);        }        public override double acceptCash(double money)        {            return money * moneyRebate;        }    }

/// 
    /// 返利收费子类    /// 
    public class CashReturn : CashSuper     {        private double moneyCondition = 0.0d;        private double moneyReturn = 0.0d;        public CashReturn(string moneyCondition,string moneyReturn)         {            this.moneyCondition = double.Parse(moneyCondition);            this.moneyReturn = double.Parse(moneyReturn);        }        public override double acceptCash(double money)        {            double result = money;            if (money >= moneyCondition) //如果大于返利条件，则需要减去返利值                result = money - Math.Floor(money/moneyCondition)*moneyReturn;            return result;        }    }

private void Form1_Load(object sender, EventArgs e)        {            comboBox1.Items.AddRange(new object[] { "正常收费", "满300返100", "打8折"});            comboBox1.SelectedIndex = 0;        }        double total = 0.0d;        private void button1_Click(object sender, EventArgs e)        {            listBox1.Items.Clear();            CashSuper csuper = CashFactory.CreateCashAccept(comboBox1.SelectedItem.ToString());            double totalPrices = 0d;            totalPrices = csuper.acceptCash(Convert.ToDouble(txtPrice.Text))*Convert.ToDouble(txtCount.Text);            total = total + totalPrices;            listBox1.Items.Add("单价：" + txtPrice.Text + " 数量：" + txtCount.Text + " " + comboBox1.SelectedItem + " 合计：" + totalPrices.ToString());            lblTotal.Text = total.ToString();        }