C#代码：用接口模拟实现存取款及银行之间的转账

1.首先定义一个接口：声明存取金额的方法

        /// <summary>
        /// 接口
        /// </summary>
        public interface IBankAccount
        {
            /// <summary>
            /// 存入金额
            /// </summary>
            /// <param name="amount"></param>
            void PayIn(decimal amount);
            /// <summary>
            /// 取出金额
            /// </summary>
            /// <param name="amount"></param>
            /// <returns></returns>
            bool WithDraw(decimal amount);
            /// <summary>
            /// 交易金额
            /// </summary>
            decimal Balance
            {
                get;
            }
        }

2.存取款SaverAccount实现接口：

        /// <summary>
        /// 类实现接口
        /// </summary>
        public class SaverAccount : IBankAccount
        {
            private decimal balance;
            /// <summary>
            /// 存款
            /// </summary>
            /// <param name="amount"></param>
            public void PayIn(decimal amount)
            {
                balance += amount;
            }

            /// <summary>
            /// 取款
            /// </summary>
            /// <param name="amount"></param>
            /// <returns></returns>
            public bool WithDraw(decimal amount)
            {
                if (balance > amount)
                {
                    balance -= amount;
                    return true;
                }
                MessageBox.Show("取款金额大于账户余额");
                return false;
            }

            /// <summary>
            /// 账户当前金额
            /// </summary>
            public decimal Balance
            {
                get
                {
                    return balance;
                }
            }

            /// <summary>
            /// 格式化输出结果
            /// </summary>
            /// <returns></returns>
            public override string ToString()
            {
                return string.Format("Venus Bank Saver:Balance={0,6:C}", balance);
            }
        }

3.定义一个转账的接口：

       public interface ITransferBankAccount : IBankAccount
        {
            bool TransferTo(IBankAccount description, decimal amount);
        }

4.实现转账接口转账的类：

 public class CurrentAccoount : ITransferBankAccount
        {
            public void PayIn(decimal amount)
            {
                balance += amount;
            }

            public bool WithDraw(decimal amount)
            {
                if (balance > amount)
                {
                    balance -= amount;
                    return true;
                }
                MessageBox.Show("取款金额大于账户余额");
                return false;
            }

            private decimal balance;
            /// <summary>
            /// 当前余额
            /// </summary>
            public decimal Balance
            {
                get
                {
                    return balance;
                }
            }

            public override string ToString()
            {
                return string.Format("YMW Bank Saver:Balance={0,6:C}", balance);
            }

            /// <summary>
            /// 转账 从当前账户转入指定账户
            /// </summary>
            /// <param name="description">转入指定帐户</param>
            /// <param name="amount">转入的金额</param>
            /// <returns>bool</returns>
            public bool TransferTo(IBankAccount description, decimal amount)
            {
                bool result = true;
                if ((result == WithDraw(amount)) == true)
                {
                    description.PayIn(amount);
                }
                return false;
            }
        }

5.测试存取款：如下

     IBankAccount iba = new SaverAccount();
     iba.PayIn(200);                                    //存入200元
     iba.WithDraw(100);                              //取出100元  
     MessageBox.Show(iba.ToString());        //账户余额100元
     MessageBox.Show("账户余额:" + iba.Balance.ToString());

6.测试转账：如下

            IBankAccount IBA = new SaverAccount();
            ITransferBankAccount ITB = new CurrentAccoount();
            IBA.PayIn(200);  //A账户存入200元
            ITB.PayIn(500);  //B账户存入500元
            ITB.TransferTo(IBA, 400);  //B账户向A账户转入400元
            MessageBox.Show(IBA.ToString());  //A账户余额600元
            MessageBox.Show(ITB.ToString());  //B账户余额100元