我正在尝试一些与C＃线程中的锁和互斥相关的概念。但是，如果发现使用Mutex可以给我正确的结果，而使用锁则不能令人满意。

使用lock构造：

class Bankaccount
{
  private int balance;
  public object padlock = new object();
  public int Balance { get => balance; private set => balance = value; }

  public void Deposit(int amount)
  {
    lock ( padlock )
    {
      balance += amount;
    }
  }

  public void Withdraw(int amount)
  {
    lock ( padlock )
    {
      balance -= amount;
    }
  }

  public void Transfer(Bankaccount where,int amount)
  {
    lock ( padlock )
    {
      balance = balance - amount;
      where.Balance = where.Balance + amount;
    }
  }
}

static void Main(string[] args)
{
  var ba1 = new Bankaccount();
  var ba2 = new Bankaccount();

  var task = Task.Factory.StartNew(() =>
  {
    for ( int j = 0; j < 1000; ++j )
      ba1.Deposit(100);
  });

  var task1 = Task.Factory.StartNew(() =>
  {
    for ( int j = 0; j < 1000; ++j )
      ba2.Deposit(100);
  });

  var task2 = Task.Factory.StartNew(() =>
  {
    for ( int j = 0; j < 1000; ++j )
      ba1.Transfer(ba2,100);
  });

  Task.WaitAll(task,task1,task2);
  Console.WriteLine($"Final balance is {ba1.Balance}.");
  Console.WriteLine($"Final balance is {ba2.Balance}.");
  Console.ReadLine();
}

在ba2设置为0的情况下，代码为ba1提供了不正确的余额。 即使每个操作都被lock语句包围，情况仍然如此。它无法正常工作。

使用Mutex构造：

class Bankaccount
{
  private int balance;

  public int Balance { get => balance; private set => balance = value; }

  public void Deposit(int amount)
  {
    balance += amount;
  }

  public void Withdraw(int amount)
  {
    balance -= amount;
  }

  public void Transfer(Bankaccount where,int amount)
  {
    balance = balance - amount;
    where.Balance = where.Balance + amount;
  }
}

static void Main(string[] args)
{
  var ba1 = new Bankaccount();
  var ba2 = new Bankaccount();

  var mutex1 = new Mutex();
  var mutex2 = new Mutex();

  var task = Task.Factory.StartNew(() =>
  {
    for ( int j = 0; j < 1000; ++j )
    {
      var lockTaken = mutex1.WaitOne();

      try
      {
        ba1.Deposit(100);
      }
      finally
      {
        if ( lockTaken )
        {
          mutex1.ReleaseMutex();
        }
      }
    }
  });

  var task1 = Task.Factory.StartNew(() =>
  {
    for ( int j = 0; j < 1000; ++j )
    {
      var lockTaken = mutex2.WaitOne();

      try
      {
        ba2.Deposit(100);
      }
      finally
      {
        if ( lockTaken )
        {
          mutex2.ReleaseMutex();
        }
      }
    }
  });

  var task2 = Task.Factory.StartNew(() =>
  {
    for ( int j = 0; j < 1000; ++j )
    {
      bool haveLock = Mutex.WaitAll(new[] { mutex1,mutex2 });
      try
      {
        ba1.Transfer(ba2,100);
      }
      finally
      {
        if ( haveLock )
        {
          mutex1.ReleaseMutex();
          mutex2.ReleaseMutex();
        }
      }
    }
  });

  Task.WaitAll(task,task2);
  Console.WriteLine($"Final balance is {ba1.Balance}.");
  Console.WriteLine($"Final balance is {ba2.Balance}.");
  Console.ReadLine();
}

通过这种方法，每次运行时我都会获得正确的余额。

我无法弄清楚为什么第一种方法无法正常工作。我是否在锁定语句方面缺少某些东西？