C＃中的多線程與Win.Forms控件

Question

我是C＃的初學者。當我使用win.forms時，線程出現問題。我的應用程序凍結。這個代碼有什麼問題？我正在使用msdn的微軟示例。 這裏是我的代碼：

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

有一個僵局 - UI線程在等待線程與Thread.Join()完成而工作線程試圖使用阻塞Control.Invoke()發送消息給UI。在通過的BeginInvoke（線程代碼）更換調用會使僵局消失

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

凍結，因爲加入的呼叫。 Thread.Join（）使當前線程在另一個完成後等待。