C# 中的多线程与 Win.Forms 控件

Question

我是 C# 的初学者。当我使用 win.forms 时，我遇到了线程问题。我的应用程序冻结。这段代码有什么问题？我正在使用来自msdn 的微软示例。 这是我的代码：

    delegate void SetTextCallback(object text);

    private void WriteString(object text)
    {
        // InvokeRequired required compares the thread ID of the 
        // calling thread to the thread ID of the creating thread. 
        // If these threads are different, it returns true. 
        if (this.textBox1.InvokeRequired)
        {
            SetTextCallback d = new SetTextCallback(WriteString);
            this.Invoke(d, new object[] { text });
        }
        else
        {
            for (int i = 0; i <= 1000; i++)
            {
                this.textBox1.Text = text.ToString();
            }
        }
    }

    private void button1_Click(object sender, EventArgs e)
    {

        Thread th_1 = new Thread(WriteString);
        Thread th_2 = new Thread(WriteString);
        Thread th_3 = new Thread(WriteString);
        Thread th_4 = new Thread(WriteString);

        th_1.Priority = ThreadPriority.Highest; // самый высокий
        th_2.Priority = ThreadPriority.BelowNormal; // выше среднего
        th_3.Priority = ThreadPriority.Normal; // средний
        th_4.Priority = ThreadPriority.Lowest; // низкий

        th_1.Start("1");
        th_2.Start("2");
        th_3.Start("3");
        th_4.Start("4");

        th_1.Join();
        th_2.Join();
        th_3.Join();
        th_4.Join();
    }

Answer 1

有一个死锁 - UI 线程正在等待线程以 Thread.Join() 完成，而工作线程正在尝试使用阻塞 Control.Invoke() 向 UI 发送消息。用 BeginInvoke() 替换线程代码中的 Invoke 将使死锁消失

 if (this.textBox1.InvokeRequired)
    {
        SetTextCallback d = new SetTextCallback(WriteString);
        // BeginInvoke posts message to UI thread asyncronously
        this.BeginInvoke(d, new object[] { text }); 
    }
    else
    {
        this.textBox1.Text = text.ToString();
    }

Answer 2

由于加入调用而冻结。 Thread.Join() 让当前线程在另一个线程完成后等待。