初学者急求：不会实现接口成员
代码如下：
using System.Collections.Generic;
using System.Text;
using Wrox.ProCSharp;
using Wrox.ProCSharp.VenusBank;
using Wrox.ProCSharp.JupiterBank;

namespace Wrox.ProCSharp
{
  public interface lBankAccount
  {
  void PayIn(decimal amount);
  bool WithDraw(decimal amount);
  decimal Balance
  {
  get;
  }
  }
}


namespace Wrox.ProCSharp.VenusBank
{
  public class SaverAccount : lBankAccount
  {
  private decimal banlance;

  public void PayIn(decimal amount)
  {
  banlance += amount;
  }

  public bool Withdraw(decimal amount)
  {
  if(banlance>=amount)
  {
  banlance -= amount ;
  return true;
  }

  Console.WriteLine("withDraw attempt failed");
  return false;
  }
   
  public decimal Banlance
  {
  get
  {
  return banlance;
  }
  }

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


namespace Wrox.ProCSharp.JupiterBank
{
  public class GoldAccount : lBankAccount 
  {

  }
}


namespace ConsoleApplication1
{
  class Program
  {
  static void Main(string[] args)
  {
  lBankAccount venusAccount = new SaverAccount();
  lBankAccount jupiterAccount = new GoldAccount();
  venusAccount.PayIn(200);
  venusAccount.WithDraw(100);
  Console.WriteLine(venusAccount.ToString());
  jupiterAccount.PayIn(500);
  jupiterAccount.WithDraw(600);
  jupiterAccount.WithDraw(100);
  Console.WriteLine(jupiterAccount.ToString());
  }
  }
}


出错：
错误 1 “Wrox.ProCSharp.VenusBank.SaverAccount”不会实现接口成员“Wrox.ProCSharp.lBankAccount.WithDraw(decimal)” d:\wody\Projects\form\ConsoleApplication1\ConsoleApplication1\Program.cs 24 18 ConsoleApplication1
错误 2 “Wrox.ProCSharp.VenusBank.SaverAccount”不会实现接口成员“Wrox.ProCSharp.lBankAccount.Balance” d:\wody\Projects\form\ConsoleApplication1\ConsoleApplication1\Program.cs 24 18 ConsoleApplication1
错误 3 “Wrox.ProCSharp.JupiterBank.GoldAccount”不会实现接口成员“Wrox.ProCSharp.lBankAccount.PayIn(decimal)” d:\wody\Projects\form\ConsoleApplication1\ConsoleApplication1\Program.cs 63 18 ConsoleApplication1
错误 4 “Wrox.ProCSharp.JupiterBank.GoldAccount”不会实现接口成员“Wrox.ProCSharp.lBankAccount.WithDraw(decimal)” d:\wody\Projects\form\ConsoleApplication1\ConsoleApplication1\Program.cs 63 18 ConsoleApplication1
错误 5 “Wrox.ProCSharp.JupiterBank.GoldAccount”不会实现接口成员“Wrox.ProCSharp.lBankAccount.Balance” d:\wody\Projects\form\ConsoleApplication1\ConsoleApplication1\Program.cs 63 18 ConsoleApplication1


------解决方案--------------------
using System.Collections.Generic; 
using System.Text; 
using Wrox.ProCSharp; 
using Wrox.ProCSharp.VenusBank; 
using Wrox.ProCSharp.JupiterBank; 

namespace Wrox.ProCSharp 
{