frmmorethreads.cs

清华大学出版社出版的 移动应用开发宝典 张大威（2008）的附书源代码

using System;
using System.Windows.Forms;
using System.Threading;
using System.Diagnostics;
using System.Collections.Generic;

namespace CodeForChapter11cs
{
  public partial class frmMoreThreads : Form
  {
    public frmMoreThreads()
    {
      InitializeComponent();
    }

    long someCounter = 0;

    private void button1_Click(object sender, EventArgs e)
    {
      someCounter = 0;
      Thread t1 = new Thread(this.ThreadBoth); // this.ThreadFirst1);
      t1.Name = "Worker Thread 1 ";
      Thread t2 = new Thread(this.ThreadBoth); // this.ThreadSecond2);
      t2.Name = "Worker Thread 2 ";

      t1.Start();
      t2.Start();

      t1.Join();
      t2.Join();

      MessageBox.Show("Final result = " + someCounter.ToString());
    }

    #region race condition 1
    private void ThreadFirst1()
    {
      for (long j = 0; j < 100000000; j++)
      {
        Debug.WriteLine(Thread.CurrentThread.Name + "before inc");
        someCounter += 1;
      }
      MessageBox.Show(Thread.CurrentThread.Name, "Done");
    }

    private void ThreadSecond2()
    {
      for (long j = 0; j < 100000000; j++)
      {
        Debug.WriteLine(Thread.CurrentThread.Name + "before inc");
        someCounter -= 1;
      }
      MessageBox.Show(Thread.CurrentThread.Name, "Done");
    }
    #endregion

    private void ThreadBoth()
    {
      Debug.WriteLine(Thread.CurrentThread.Name + "enters method");
      int localVar = 0;
      localVar += 1;

      //lock (someLock) // uncomment the lock region to achieve the undesired effects
      //{
        if (someCounter == 0)
        {
          Debug.WriteLine(Thread.CurrentThread.Name + "in if block");
          Thread.Sleep(1); //simulate some longer activity
          someCounter += localVar;
          Debug.WriteLine(Thread.CurrentThread.Name + "just incremented");
        }
        else
        {
          Debug.WriteLine(Thread.CurrentThread.Name + "in else block");
          someCounter += 3;
        }
      //} // end lock
      return;
    }

    #region Not used in sample. Shows Monitor code
    object someLock = new object();
    private void SomeMethod()
    {
      // some code

      Monitor.Enter(this);
      try
      {
        // critical region, only 1 thread at a time enters this

      }
      finally
      {
        Monitor.Exit(this);
      }

      // other code
    }
    
    #endregion
  }
}