新线程中的WebBrowser控件

您必须创建一个sta线程,该线程会产生一个消息循环。对于像WebBrowser这样的ActiveX组件来说,这是唯一友好的环境。否则将无法获取DocumentCompleted事件。一些示例代码:

private void runBrowserThread(Uri url) {
    var th = new Thread(() => {
        var br = new WebBrowser();
        br.DocumentCompleted += browser_DocumentCompleted;
        br.Navigate(url);
        Application.Run();
    });
    th.SetApartmentState(ApartmentState.STA);
    th.Start();
}

void browser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) {
    var br = sender as WebBrowser;
    if (br.Url == e.Url) {
        Console.WriteLine("Natigated to {0}", e.Url);
        Application.ExitThread();   // Stops the thread
    }
}

以下是如何在非UI线程上组织消息循环,以运行异步任务,如 WebBrowser 自动化。它使用 async/await 提供方便的线性代码流并在循环中加载一组网页。该代码是一个随时可以运行的控制台应用程序,部分基于 this excellent post .

相关答案:

• https://stackoverflow.com/a/22262976/1768303
• https://stackoverflow.com/a/21775343/1768303

using System;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace ConsoleApplicationWebBrowser
{
    // by Noseratio - https://stackoverflow.com/users/1768303/noseratio
    class Program
    {
        // Entry Point of the console app
        static void Main(string[] args)
        {
            try
            {
                // download each page and dump the content
                var task = MessageLoopWorker.Run(DoWorkAsync,
                    "http://www.example.com", "http://www.example.net", "http://www.example.org");
                task.Wait();
                Console.WriteLine("DoWorkAsync completed.");
            }
            catch (Exception ex)
            {
                Console.WriteLine("DoWorkAsync failed: " + ex.Message);
            }

            Console.WriteLine("Press Enter to exit.");
            Console.ReadLine();
        }

        // navigate WebBrowser to the list of urls in a loop
        static async Task<object> DoWorkAsync(object[] args)
        {
            Console.WriteLine("Start working.");

            using (var wb = new WebBrowser())
            {
                wb.ScriptErrorsSuppressed = true;

                TaskCompletionSource<bool> tcs = null;
                WebBrowserDocumentCompletedEventHandler documentCompletedHandler = (s, e) =>
                    tcs.TrySetResult(true);

                // navigate to each URL in the list
                foreach (var url in args)
                {
                    tcs = new TaskCompletionSource<bool>();
                    wb.DocumentCompleted += documentCompletedHandler;
                    try
                    {
                        wb.Navigate(url.ToString());
                        // await for DocumentCompleted
                        await tcs.Task;
                    }
                    finally
                    {
                        wb.DocumentCompleted -= documentCompletedHandler;
                    }
                    // the DOM is ready
                    Console.WriteLine(url.ToString());
                    Console.WriteLine(wb.Document.Body.OuterHtml);
                }
            }

            Console.WriteLine("End working.");
            return null;
        }

    }

    // a helper class to start the message loop and execute an asynchronous task
    public static class MessageLoopWorker
    {
        public static async Task<object> Run(Func<object[], Task<object>> worker, params object[] args)
        {
            var tcs = new TaskCompletionSource<object>();

            var thread = new Thread(() =>
            {
                EventHandler idleHandler = null;

                idleHandler = async (s, e) =>
                {
                    // handle Application.Idle just once
                    Application.Idle -= idleHandler;

                    // return to the message loop
                    await Task.Yield();

                    // and continue asynchronously
                    // propogate the result or exception
                    try
                    {
                        var result = await worker(args);
                        tcs.SetResult(result);
                    }
                    catch (Exception ex)
                    {
                        tcs.SetException(ex);
                    }

                    // signal to exit the message loop
                    // Application.Run will exit at this point
                    Application.ExitThread();
                };

                // handle Application.Idle just once
                // to make sure we're inside the message loop
                // and SynchronizationContext has been correctly installed
                Application.Idle += idleHandler;
                Application.Run();
            });

            // set STA model for the new thread
            thread.SetApartmentState(ApartmentState.STA);

            // start the thread and await for the task
            thread.Start();
            try
            {
                return await tcs.Task;
            }
            finally
            {
                thread.Join();
            }
        }
    }
}

根据我过去的经验,WebBrowser不喜欢在主应用程序线程之外操作。

尝试使用httpwebrequests,您可以将其设置为异步的,并创建响应的处理程序,以了解响应何时成功。完整:

how-to-use-httpwebrequest-net-asynchronously

一种简单的解决方案,其中多个WebBrowser同时运行。

1. 创建新的Windows窗体应用程序
2. 放置名为的按钮 钮扣1
3. 放置名为text box 1的文本框
4. 设置文本属性 字段:多行真和滚动条

5. 写下以下内容 按钮1单击处理程序:

   textBox1.Clear();
   textBox1.AppendText(DateTime.Now.ToString() + Environment.NewLine);
   int completed_count = 0;
   int count = 10;
   for (int i = 0; i < count; i++)
   {
       int tmp = i;
       this.BeginInvoke(new Action(() =>
       {
           var wb = new WebBrowser();
           wb.ScriptErrorsSuppressed = true;
           wb.DocumentCompleted += (cur_sender, cur_e) =>
           {
               var cur_wb = cur_sender as WebBrowser;
               if (cur_wb.Url == cur_e.Url)
               {
                   textBox1.AppendText("Task " + tmp + ", navigated to " + cur_e.Url + Environment.NewLine);
                   completed_count++;
               }
           };
           wb.Navigate("https://stackoverflow.com/questions/4269800/webbrowser-control-in-a-new-thread");
       }
       ));
   }
   
   while (completed_count != count)
   {
       Application.DoEvents();
       Thread.Sleep(10);
   }
   textBox1.AppendText("All completed" + Environment.NewLine);