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跨线程调用窗体控件

何以:对 Windows 窗体控件进行线程安全调用

做客 Windows 窗体控件本质上不是线程安全的。 假使有八个或多个线程操作某意气风发控件的景况,则大概会倒逼该控件走入后生可畏种区别等的事态。 还会产出别的与线程相关的 Bug,比方争用状态和死锁。 确定保证以线程安全情势访谈控件特别主要。

在未使用 Invoke.aspx)方法的意况下,从不是创办某些控件的线程的任何线程调用该控件是不安全的。 以下非线程安全的调用的亲自过问。

        // This event handler creates a thread that calls a 
        // Windows Forms control in an unsafe way.
        private void setTextUnsafeBtn_Click(
            object sender, 
            EventArgs e)
        {
            this.demoThread = 
                new Thread(new ThreadStart(this.ThreadProcUnsafe));
            this.demoThread.Start();
        }
        // This method is executed on the worker thread and makes
        // an unsafe call on the TextBox control.
        private void ThreadProcUnsafe()
        {
            this.textBox1.Text = "This text was set unsafely.";
        }

.NET Framework 可扶持你检查评定以非线程安全情势访谈控件这一难题。 在调节和测验器中运作应用程序时,假设贰个不是创造有些控件的线程的任何线程调用该控件,则调节和测验器会掀起一个 InvalidOperationException.aspx卡塔尔(قطر‎,并体现以下音讯:“从不是创建控件控件名称 的线程访问它。”

此非常在调试时期和周转时的少数意况下可相信地发生。 在调节和测量检验以 .NET Framework 2.0 版此前的 .NET Framework 编写的应用程序时,恐怕会出现此充裕。 大家猛烈提议您在意识此难题时张开修补,但你能够透过将 CheckForIllegalCrossThreadCalls.aspx卡塔尔国属性设置为 false 来禁止使用它。(不推荐)


对 Windows 窗体控件举办线程安全调用

  1. 查询控件的 InvokeRequired.aspx) 属性。

  2. 如果 InvokeRequired.aspx)重临 true,则利用实际调用控件的寄托来调用 Invoke.aspx)。

  3. 如果 InvokeRequired.aspx卡塔尔国重回 false,则一向调用控件。

  在上面包车型地铁代码示例中,将要由后台线程实行的 ThreadProcSafe 方法中落实线程安全调用。 假如 TextBox.aspx) 控件的 InvokeRequired.aspx卡塔尔(قطر‎再次回到 true,则 ThreadProcSafe 方法会创立 SetTextCallback 的二个实例,并将该实例传递给窗体的 Invoke.aspxState of Qatar方法。 那使得 SetText 方法被创设 跨线程调用窗体控件。TextBox.aspx卡塔尔国控件的线程调用,何况在那线程上下文少校直接设置 Text.aspx) 属性。

       // This event handler creates a thread that calls a 
        // Windows Forms control in a thread-safe way.
        private void setTextSafeBtn_Click(
            object sender, 
            EventArgs e)
        {
               this.demoThread = 
               new Thread(new ThreadStart(this.ThreadProcSafe));
               this.demoThread.Start();
        }

        // This method is executed on the worker thread and makes
        // a thread-safe call on the TextBox control.
        private void ThreadProcSafe()
        {
            this.SetText("This text was set safely.");
        }

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

namespace CrossThreadDemo
{
    public class Form1 : Form
    {
        // This delegate enables asynchronous calls for setting
        // the text property on a TextBox control.
        delegate void SetTextCallback(string text);

        // This thread is used to demonstrate both thread-safe and
        // unsafe ways to call a Windows Forms control.
        private Thread demoThread = null;

        // This BackgroundWorker is used to demonstrate the 
        // preferred way of performing asynchronous operations.
        private BackgroundWorker backgroundWorker1;

        private TextBox textBox1;
        private Button setTextUnsafeBtn;
        private Button setTextSafeBtn;
        private Button setTextBackgroundWorkerBtn;

        private System.ComponentModel.IContainer components = null;

        public Form1()
        {
            InitializeComponent();
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        // This event handler creates a thread that calls a 
        // Windows Forms control in an unsafe way.
        private void setTextUnsafeBtn_Click(
            object sender, 
            EventArgs e)
        {
            this.demoThread = 
                new Thread(new ThreadStart(this.ThreadProcUnsafe));

            this.demoThread.Start();
        }

        // This method is executed on the worker thread and makes
        // an unsafe call on the TextBox control.
        private void ThreadProcUnsafe()
        {
            this.textBox1.Text = "This text was set unsafely.";
        }

        // This event handler creates a thread that calls a 
        // Windows Forms control in a thread-safe way.
        private void setTextSafeBtn_Click(
            object sender, 
            EventArgs e)
        {
            this.demoThread = 
                new Thread(new ThreadStart(this.ThreadProcSafe));

            this.demoThread.Start();
        }

        // This method is executed on the worker thread and makes
        // a thread-safe call on the TextBox control.
        private void ThreadProcSafe()
        {
            this.SetText("This text was set safely.");
        }

        // This method demonstrates a pattern for making thread-safe
        // calls on a Windows Forms control. 
        //
        // If the calling thread is different from the thread that
        // created the TextBox control, this method creates a
        // SetTextCallback and calls itself asynchronously using the
        // Invoke method.
        //
        // If the calling thread is the same as the thread that created
        // the TextBox control, the Text property is set directly. 

        private void SetText(string 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(SetText);
                this.Invoke(d, new object[] { text });
            }
            else
            {
                this.textBox1.Text = text;
            }
        }

        // This event handler starts the form's 
        // BackgroundWorker by calling RunWorkerAsync.
        //
        // The Text property of the TextBox control is set
        // when the BackgroundWorker raises the RunWorkerCompleted
        // event.
        private void setTextBackgroundWorkerBtn_Click(
            object sender, 
            EventArgs e)
        {
            this.backgroundWorker1.RunWorkerAsync();
        }

        // This event handler sets the Text property of the TextBox
        // control. It is called on the thread that created the 
        // TextBox control, so the call is thread-safe.
        //
        // BackgroundWorker is the preferred way to perform asynchronous
        // operations.

        private void backgroundWorker1_RunWorkerCompleted(
            object sender, 
            RunWorkerCompletedEventArgs e)
        {
            this.textBox1.Text = 
                "This text was set safely by BackgroundWorker.";
        }

        #region Windows Form Designer generated code

        private void InitializeComponent()
        {
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.setTextUnsafeBtn = new System.Windows.Forms.Button();
            this.setTextSafeBtn = new System.Windows.Forms.Button();
            this.setTextBackgroundWorkerBtn = new System.Windows.Forms.Button();
            this.backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
            this.SuspendLayout();
            // 
            // textBox1
            // 
            this.textBox1.Location = new System.Drawing.Point(12, 12);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(240, 20);
            this.textBox1.TabIndex = 0;
            // 
            // setTextUnsafeBtn
            // 
            this.setTextUnsafeBtn.Location = new System.Drawing.Point(15, 55);
            this.setTextUnsafeBtn.Name = "setTextUnsafeBtn";
            this.setTextUnsafeBtn.TabIndex = 1;
            this.setTextUnsafeBtn.Text = "Unsafe Call";
            this.setTextUnsafeBtn.Click += new System.EventHandler(this.setTextUnsafeBtn_Click);
            // 
            // setTextSafeBtn
            // 
            this.setTextSafeBtn.Location = new System.Drawing.Point(96, 55);
            this.setTextSafeBtn.Name = "setTextSafeBtn";
            this.setTextSafeBtn.TabIndex = 2;
            this.setTextSafeBtn.Text = "Safe Call";
            this.setTextSafeBtn.Click += new System.EventHandler(this.setTextSafeBtn_Click);
            // 
            // setTextBackgroundWorkerBtn
            // 
            this.setTextBackgroundWorkerBtn.Location = new System.Drawing.Point(177, 55);
            this.setTextBackgroundWorkerBtn.Name = "setTextBackgroundWorkerBtn";
            this.setTextBackgroundWorkerBtn.TabIndex = 3;
            this.setTextBackgroundWorkerBtn.Text = "Safe BW Call";
            this.setTextBackgroundWorkerBtn.Click += new System.EventHandler(this.setTextBackgroundWorkerBtn_Click);
            // 
            // backgroundWorker1
            // 
            this.backgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker1_RunWorkerCompleted);
            // 
            // Form1
            // 
            this.ClientSize = new System.Drawing.Size(268, 96);
            this.Controls.Add(this.setTextBackgroundWorkerBtn);
            this.Controls.Add(this.setTextSafeBtn);
            this.Controls.Add(this.setTextUnsafeBtn);
            this.Controls.Add(this.textBox1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion


        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.Run(new Form1());
        }

    }
}

 

 

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