c# lock (obj) 与 lock (this) 区别

OStack程序员社区-中国程序员成长平台 › 门户 › 编程› Node.js›Node.js教程

原作者: [db:作者] 来自: [db:来源] 收藏邀请

lock(obj) 锁定 obj 对象

lock(this) 锁定当前实例对象，如果有多个类实例的话，lock锁定的只是当前类实例，对其它类实例无影响。

直接上代码。

主窗体代码如下：

delegate void SetTextCallback(string text);
public Form1()
        {
            InitializeComponent();
        }
/// <summary>
/// 利用委托设置 文本框内容
/// </summary>
/// <param name="text"></param>
        public void SetText(string text)
        {
if (this.textBox1.InvokeRequired)
            {
                SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { text });
            }
else
            {
this.textBox1.Text = this.textBox1.Text + "\r\n" + text;
            }
        }

private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Text = "";
            Thread[] thd = new Thread[500];
int intI = 0;
for (intI = 0; intI < 50; intI++)
            {
                thd[intI] = new Thread(new ParameterizedThreadStart(thdText));
                thd[intI].Name = " Thread" + intI.ToString();
                thd[intI].IsBackground = true;
                thd[intI].Start(intI);
            }
        }
/// <summary>
/// 线程调用的方法
/// </summary>
/// <param name="obj"></param>
        private void thdText(object obj)
        {
            oper op = new oper();
int intI = Convert.ToInt32(obj);
            SetText(op.addition());
        }

1、lock(obj)

添加oper类，代码如下：

    public class oper
    {
private static object obj = new object();

private static Single slgTotal;

public string addition()
        {
lock (obj)
            {
int intI = 0;
                slgTotal = 0;
for (intI = 0; intI <= 50; intI++)
                {
                    slgTotal = slgTotal + intI;
                    Thread.Sleep(5);
                }

return slgTotal.ToString() + " thread:" + Thread.CurrentThread.Name;
            }
        }
    }

执行结果如下：

大家看到每个线程执行的结果都是相同的。下面来看lock(this)

2、lock(this)

将oper类代码修改为如下：

    public class oper
    {
private static object obj = new object();

private static Single slgTotal;

public string addition()
        {
lock (this)
            {
int intI = 0;
                slgTotal = 0;
for (intI = 0; intI <= 50; intI++)
                {
                    slgTotal = slgTotal + intI;
                    Thread.Sleep(5);
                }

return slgTotal.ToString() + " thread:" + Thread.CurrentThread.Name;
            }
        }
    }

执行结果如下：

大家看到每个线程执行的结果都是不同的。

分析：lock(this) 锁定的对象是当前类实例，而每个线程操作的都是oper的新实例,lock(this)只对当前实例起作用，而 slgTotal 是类的静态变量，lock(this)实际上是没在起起我们想要的结果。下面再看一种lock(obj)的实例

3、lock(obj) 这个第一个obj的demo稍有不同，即把oper类的obj静态变量修改为变量，oper类修改为如下：

    public class oper
    {
private object obj = new object();

private static Single slgTotal;

public string addition()
        {
lock (obj)
            {
int intI = 0;
                slgTotal = 0;
for (intI = 0; intI <= 50; intI++)
                {
                    slgTotal = slgTotal + intI;
                    Thread.Sleep(5);
                }

return slgTotal.ToString() + " thread:" + Thread.CurrentThread.Name;
            }
        }
    }