为什么新类中的计时器滴答事件会从 form1 调用一次方法，而下一次它什么也不做？

Question

在 form1 我有这个公共方法：

public void CombindedStringFix()
        {
            BeginUpdate();

            label3.Text = SaveOldHtml.HtmlLoadedFileNumber.ToString();
            richTextBox1.Clear();
            List<string> newText1 = new List<string>();
            label1.Select();
            scrollerList = new List<string>(Filters.newTextWithoutLinks);
            scrollerText = string.Join(Environment.NewLine, scrollerList);
            scroller1.TextToScroll = scrollerText;
            combindedString = string.Join(Environment.NewLine, SaveOldHtml.newText);
            richTextBox1.Text = combindedString;            
            string[] rlines = richTextBox1.Lines;
            timer3.Start();
            richTextBox1.SelectionStart = 0;
            richTextBox1.SelectionLength = rlines[0].Length;
            richTextBox1.SelectionColor = Color.Red;
            richTextBox1.Select(rlines[0].Length, rlines[1].Length + 1);
            richTextBox1.SelectionColor = Color.Green;

            EndUpdate();
        }

然后在新类中我调用这个方法：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Timers;
using System.Windows.Forms;

namespace ScrollLabelTest
{

    class SaveOldHtml
    {
        private static Form1 frm1 = null;
        private static int count;
        private static System.Timers.Timer _timer = new System.Timers.Timer();
        private static string page;
        public static List<string> newText = new List<string>();
        public static int HtmlLoadedFileNumber = 0;

        public SaveOldHtml(string DirectoryToSave,int count, string contents)
        {
            System.IO.File.WriteAllText(DirectoryToSave + "Page" + count.ToString("D6")
                                        + ".html", contents);
        }

        public SaveOldHtml(string DirectoryToSave, List<string> newTextList, int count)
        {
            using (StreamWriter myStream = new StreamWriter(DirectoryToSave + "newTextList" + count.ToString("D6")
                                        + ".txt"))
            {
                for (int i = 0; i < newTextList.Count; i++)
                {
                    myStream.WriteLine(newTextList[i]);
                }

            }
        }

        public static void Start(Form1 form)
        {
            frm1 = form;
            _timer.Elapsed += _timer_Elapsed;
            _timer.Interval = 10000;
            count = 5;
            LoadOldHtmlFiles();
            frm1.CombindedStringFix();
            _timer.Start();
        }

        static void _timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            _timer.Stop();
            LoadOldHtmlFiles();
            frm1.CombindedStringFix();
            _timer.Start();
        }

        private static void LoadOldHtmlFiles()
        {

            page = File.ReadAllText(@"c:\temp\OldHtml\page" + count.ToString("D6") + ".html");
            ListsExtractions.OffExtractions(@"c:\temp\OldHtml\page" + count.ToString("D6") + ".html", page, newText);
            count ++;
            HtmlLoadedFileNumber++;
        }
    }
}

一旦我在类的 Start 方法中调用 CombindedStringFix 方法，它就会工作并执行 CombindedStringFix 中的所有行。我使用了一个断点，它可以完成所有工作。

但是下次当它在新类中调用计时器滴答事件中的方法时，我使用了一个断点，并且一旦它执行第一行 BegingUpdate();它只是继续，永远不会在计时器滴答事件中再次停止，并且永远不会在 BeginUpdate() 之后继续；

即使我删除 BeginUpdate();所以它会做第一行然后继续它永远不会移动到下一行。

我现在看到我在计时器滴答事件中遇到异常：

跨线程操作无效：控件“Form1”从创建它的线程以外的线程访问

System.InvalidOperationException was caught
  HResult=-2146233079
  Message=Cross-thread operation not valid: Control 'Form1' accessed from a thread other than the thread it was created on.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.Control.get_Handle()
       at ScrollLabelTest.Form1.BeginUpdate() in e:\scrolllabel\ScrollLabel\ScrollLabel\Form1.cs:line 69
       at ScrollLabelTest.Form1.CombindedStringFix() in e:\scrolllabel\ScrollLabel\ScrollLabel\Form1.cs:line 280
       at ScrollLabelTest.SaveOldHtml._timer_Elapsed(Object sender, ElapsedEventArgs e) in e:\scrolllabel\ScrollLabel\ScrollLabel\SaveOldHtml.cs:line 64
  InnerException: 

我猜这与 frm1 变量有关。

Answer 1

问题很可能是在您的 Elapsed 事件中某处发生了异常，并且计时器永远不会再次启动。您可以设置一个断点并在它第一次进入时跟随它以查看它在哪里/如果它失败。或者，您可以对其进行编码以启动备份：

static void _timer_Elapsed(object sender, ElapsedEventArgs e)
{
    _timer.Stop();

    try
    {
        LoadOldHtmlFiles();
        frm1.CombindedStringFix();
    }
    catch (Exception ex)
    {
        // do something (or nothing) with the exception
    }
    finally 
    {
        _timer.Start();
    }
}

---

既然您确认发生了跨线程异常，我建议您阅读：

How to: Make Thread-Safe Calls to Windows Forms Controls

这是他们的演示，以防链接断开：

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());
        }

    }
}

Answer 2

我将尝试回答这个问题，但没有完整的上下文，这有点粗糙。

1. 我注意到，在CombindedStringFix() 方法中，您有一个似乎是名为timer3 的计时器对象。此计时器的名称似乎与您在 SaveOldHtml 类中的计时器名称不匹配，并且我没有看到该名称公开的属性/字段。我想知道您是否有两个可能会混淆的计时器。

我知道不回答这个问题是不好的形式，但在没有更多细节/更多来源的情况下，这是我能召集的最好的。更多上下文，我可以提供更多帮助！