C#多线程更新TextBox

Question

我正在制作一个简单的WinForm，该程序会启动多个线程来循环从0到10000。目的是通过减缓Windows来使其他程序运行变慢。

基本上，该表单有一个文本框，我想从每个线程将循环索引写入该文本框。当只有一个线程时一切正常，但自从我引入了更多线程后，当我点击停止按钮时，应用程序会卡住，我不确定接下来该怎么做。

我的示例可能没有编写好。我想更好地了解多线程、死锁等。我之前尝试过使用BackgroundWorker，但在过去的两年中，我一直在使用Java。

public delegate void SetTextDelegate(string text);

public partial class Form1 : Form
{
    private Thread[] _slow;
    private object lockTextBox = new object();

    public Form1()
    {
        InitializeComponent();
    }

    #region Event Handlers

    private void ui_btnClose_Click(object sender, EventArgs e)
    {
        this.Close();
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void ui_btnStart_Click(object sender, EventArgs e)
    {
        if (_slow != null)
        {
            StopAllThreads();
        }

        _slow = new Thread[ (int) numNoOfTheads.Value ];
        for( int i = 0; i < numNoOfTheads.Value; i++)
        {
            _slow[i] = new Thread(ThreadRunLoop);
            _slow[i].Start();
        }
    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        if (_slow != null)
        {
            StopAllThreads();
        }
    }

    private void ui_btnStop_Click(object sender, EventArgs e)
    {
        if (_slow != null)
        {
            StopAllThreads();
        }
    }

    private void ui_btnClear_Click(object sender, EventArgs e)
    {
        this.textBox1.Clear();
    }

    #endregion

    protected void ThreadRunLoop()
    {
        try
        {
            for (int i = 0; i < 10000; i++)
            {
                UpdateText("Loop " + i + " for " + Thread.CurrentThread.ManagedThreadId);
            }
        }
        catch (ThreadInterruptedException ex)
        {
            Console.WriteLine("Thread has been interrupted.");
        }
    }

    private void UpdateText(string text)
    {
        //lock (lockTextBox)
        //{
            if (textBox1.InvokeRequired)
            {
                textBox1.Invoke(new SetTextDelegate(UpdateText), text);
            }
            else
            {
                textBox1.SuspendLayout();
                textBox1.Text = textBox1.Text + text + System.Environment.NewLine;
                textBox1.SelectionStart = textBox1.Text.Length;
                textBox1.ScrollToCaret();
                textBox1.ResumeLayout();

            }
        //}
    }

    private void StopAllThreads()
    {
        for (int i = 0; i < _slow.Length; i++)
        {
            if (_slow[i] != null)
            {
                _slow[i].Interrupt();
                _slow[i] = null;
            }
        }
        _slow = null;
    }
}

Form1.Designer.cs

partial class Form1
{
    /// <summary>
    /// Required designer variable.
    /// </summary>
    private System.ComponentModel.IContainer components = null;

    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
    protected override void Dispose(bool disposing)
    {
        if (disposing && (components != null))
        {
            components.Dispose();
        }
        base.Dispose(disposing);
    }

    #region Windows Form Designer generated code

    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        this.ui_btnClose = new System.Windows.Forms.Button();
        this.ui_btnStart = new System.Windows.Forms.Button();
        this.ui_btnStop = new System.Windows.Forms.Button();
        this.textBox1 = new System.Windows.Forms.TextBox();
        this.ui_btnClear = new System.Windows.Forms.Button();
        this.numNoOfTheads = new System.Windows.Forms.NumericUpDown();
        this.label1 = new System.Windows.Forms.Label();
        ((System.ComponentModel.ISupportInitialize)(this.numNoOfTheads)).BeginInit();
        this.SuspendLayout();
        // 
        // ui_btnClose
        // 
        this.ui_btnClose.Location = new System.Drawing.Point(433, 268);
        this.ui_btnClose.Name = "ui_btnClose";
        this.ui_btnClose.Size = new System.Drawing.Size(75, 23);
        this.ui_btnClose.TabIndex = 0;
        this.ui_btnClose.Text = "Close";
        this.ui_btnClose.UseVisualStyleBackColor = true;
        this.ui_btnClose.Click += new System.EventHandler(this.ui_btnClose_Click);
        // 
        // ui_btnStart
        // 
        this.ui_btnStart.Location = new System.Drawing.Point(12, 12);
        this.ui_btnStart.Name = "ui_btnStart";
        this.ui_btnStart.Size = new System.Drawing.Size(75, 23);
        this.ui_btnStart.TabIndex = 1;
        this.ui_btnStart.Text = "Start";
        this.ui_btnStart.UseVisualStyleBackColor = true;
        this.ui_btnStart.Click += new System.EventHandler(this.ui_btnStart_Click);
        // 
        // ui_btnStop
        // 
        this.ui_btnStop.Location = new System.Drawing.Point(12, 41);
        this.ui_btnStop.Name = "ui_btnStop";
        this.ui_btnStop.Size = new System.Drawing.Size(75, 23);
        this.ui_btnStop.TabIndex = 2;
        this.ui_btnStop.Text = "Stop";
        this.ui_btnStop.UseVisualStyleBackColor = true;
        this.ui_btnStop.Click += new System.EventHandler(this.ui_btnStop_Click);
        // 
        // textBox1
        // 
        this.textBox1.Location = new System.Drawing.Point(93, 12);
        this.textBox1.Multiline = true;
        this.textBox1.Name = "textBox1";
        this.textBox1.ScrollBars = System.Windows.Forms.ScrollBars.Both;
        this.textBox1.Size = new System.Drawing.Size(415, 241);
        this.textBox1.TabIndex = 3;
        // 
        // ui_btnClear
        // 
        this.ui_btnClear.Location = new System.Drawing.Point(352, 268);
        this.ui_btnClear.Name = "ui_btnClear";
        this.ui_btnClear.Size = new System.Drawing.Size(75, 23);
        this.ui_btnClear.TabIndex = 4;
        this.ui_btnClear.Text = "Clear";
        this.ui_btnClear.UseVisualStyleBackColor = true;
        this.ui_btnClear.Click += new System.EventHandler(this.ui_btnClear_Click);
        // 
        // numNoOfTheads
        // 
        this.numNoOfTheads.Location = new System.Drawing.Point(12, 98);
        this.numNoOfTheads.Name = "numNoOfTheads";
        this.numNoOfTheads.Size = new System.Drawing.Size(74, 20);
        this.numNoOfTheads.TabIndex = 5;
        this.numNoOfTheads.Value = new decimal(new int[] {
        1,
        0,
        0,
        0});
        // 
        // label1
        // 
        this.label1.AutoSize = true;
        this.label1.Location = new System.Drawing.Point(9, 82);
        this.label1.Name = "label1";
        this.label1.Size = new System.Drawing.Size(83, 13);
        this.label1.TabIndex = 6;
        this.label1.Text = "No. Of Threads:";
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(520, 303);
        this.Controls.Add(this.label1);
        this.Controls.Add(this.numNoOfTheads);
        this.Controls.Add(this.ui_btnClear);
        this.Controls.Add(this.textBox1);
        this.Controls.Add(this.ui_btnStop);
        this.Controls.Add(this.ui_btnStart);
        this.Controls.Add(this.ui_btnClose);
        this.Name = "Form1";
        this.Text = "Slow My Machine";
        this.Load += new System.EventHandler(this.Form1_Load);
        this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.Form1_FormClosing);
        ((System.ComponentModel.ISupportInitialize)(this.numNoOfTheads)).EndInit();
        this.ResumeLayout(false);
        this.PerformLayout();

    }

    #endregion

    private System.Windows.Forms.Button ui_btnClose;
    private System.Windows.Forms.Button ui_btnStart;
    private System.Windows.Forms.Button ui_btnStop;
    private System.Windows.Forms.TextBox textBox1;
    private System.Windows.Forms.Button ui_btnClear;
    private System.Windows.Forms.NumericUpDown numNoOfTheads;
    private System.Windows.Forms.Label label1;
}

如果我将锁移动到UpdateText方法中的else语句，并在循环中添加Thread.Sleep(20);，则我的GUI更加响应，我可以点击停止按钮并移动窗体。欢迎提供任何反馈和修复建议。

- Andez

---

这可能是一个不好的答案，或者根本不是答案。为什么不将更新函数设为同步函数呢？ - Aadi Droid

仍然有很多线程的相同效果。 - Andez

好的，所以你正在进行阻塞调用，这就是为什么用户界面会冻结，将阻塞函数改为异步调用。 - Aadi Droid

Answer 1

UpdateText 中的 lock 会导致死锁。工作线程获取锁并调用 Invoke，然后UI线程尝试获取 相同的 锁，但必须等待直到它被释放。问题是锁永远不会被释放，因为 Invoke 会阻塞直到UI线程执行委托完毕。这从未发生过，因为UI线程仍在等待获取锁。死锁！

- Brian Gideon

---

谢谢那个信息，Brian +1 - Andez

Answer 2

将for循环更改为

   for (int i = 0; i < 10000; i++)
    {
       var text = "Loop " + i + " for " + Thread.CurrentThread.ManagedThreadId;
       if (textBox1.InvokeRequired)
          textBox1.Invoke(new SetTextDelegate(UpdateText), text);
       else
          UpdateText(text);
    }

将UpdateText更改为

    private void UpdateText(string text)
    {
       textBox1.SuspendLayout();
       textBox1.Text = textBox1.Text + text + System.Environment.NewLine;
       textBox1.SelectionStart = textBox1.Text.Length;
       textBox1.ScrollToCaret();
       textBox1.ResumeLayout();
     }

编辑：我犯了一个错误。这只会改善组织，而不会在任何方面改善。如果您想频繁更新 UI，则应使用 BackgroundWorker（如 rdkleine 所说）。

- Prakash

---

不太确定那有什么帮助，抱歉。这只是将UpdateText调用移入循环中吗？ - Andez

@Andez 抱歉，这是我的错误。我修改了答案。 - Prakash

Answer 3

尝试将UpdateText中的锁移到else内部。

- Polyfun

---

尝试过那种方法，但是界面会变得无响应，你无法移动窗体或者点击停止按钮。 - Andez

我可以在循环中添加Thread.Sleep(20)，这样可以使表单更加响应。这对于2个线程来说还可以，但如果有8个线程，我又回到了表单不响应的主要问题。 - Andez

在这种情况下，Application.DoEvents(); 可能比 Thread.Sleep(); 更好。 - paul

是的，我的错误 - UpdateText 应该是单线程的，所以你不需要使用锁。 - Polyfun

Answer 4

使用一个 BackgroundWorker 来更新 UI 线程。

这里有一个很好的例子来演示如何使用 BackgroundWorker：

http://msdn.microsoft.com/en-us/library/cc221403(v=vs.95).aspx

这并没有解释如何检索数据（您的int值）并将其放入文本框，但这是一个好的开始。

- Ralf de Kleine