WPF中的BackgroundWorker不工作[重复]

Question

我有一个导航网页的按钮。我试图将导航放在后台工作人员中，但它不能导航。如果我把它放在按钮的点击事件中它工作正常。我在 bgw_DoWork 中放置了一个断点，它表明它达到了创建新 wb 对象的目的，但是它跳过了 DoWork 中的其余语句。我想这样做，以便在尝试从网页获取数据时显示加载图像。 webbrowser 对象不是 UI 的一部分，因为用户不需要查看抓取。它只是将信息下载到一个对象中，然后再显示该对象（在 BackgroundWorker 之外）。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.Windows;
using System.Windows.Threading;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Reflection;
using System.ComponentModel;
using mshtml;

namespace WPF1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {


        WebBrowser wb;
        private readonly BackgroundWorker bgw = new BackgroundWorker();

        public int i = 0;

        public MainWindow()
        {
            InitializeComponent();
            bgw.DoWork += bgw_DoWork;
            bgw.RunWorkerCompleted += bgw_RunWorkerCompleted;

       }

        private void GetSICData_Click(object sender, RoutedEventArgs e)
        {
            //mainTabControl.SelectedIndex = 1;

            //wb.Navigated += wb_Navigated;
            //wb.LoadCompleted += wb_LoadCompleted;
            //wb.Navigate("http://www.google.com");

            bgw.RunWorkerAsync();

        }

        private void bgw_DoWork(object sender, DoWorkEventArgs e)
        {
            wb = new WebBrowser();

            wb.Navigated += wb_Navigated;
            wb.LoadCompleted += wb_LoadCompleted;
            wb.Navigate("http://www.google.com");

        }

        private void bgw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            MessageBox.Show("Background Complete");
        }

        void wb_LoadCompleted(object sender, NavigationEventArgs e)
        {

            HTMLDocument doc = (HTMLDocument)wb.Document;
            doc.getElementById("ctl03_TextBox1").innerText = "2334882";

            wb.LoadCompleted -= wb_LoadCompleted;
            wb.LoadCompleted += wb_LoadCompleted_2;

            doc.getElementById("ImageButton1").click();

        }

        void wb_LoadCompleted_2(object sender, NavigationEventArgs e)
        {
            MessageBox.Show("It Worked!");
        }

        void wb_Navigated(object sender, NavigationEventArgs e)
        {

        }

    }
}

Answer 1

听起来你真正想要的是WebClient Class。您可以使用它的多种方法将整个网页下载为文件或string。最好的部分是您也可以异步执行此操作，因此这一切都会自动在后台线程上发生。

在使用这些异步方法时，您需要处理相关的Download...Completed 事件来检索结果。来自 MSDN 上的DownloadStringCompletedEventHandler Delegate 页面：

public static void DownloadStringInBackground2 (string address)
{
    WebClient client = new WebClient ();
    Uri uri = new Uri(address);

    // Specify that the DownloadStringCallback2 method gets called 
    // when the download completes.
    client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(
DownloadStringCallback2);
    client.DownloadStringAsync (uri);
}

private static void DownloadStringCallback2 (Object sender, 
DownloadStringCompletedEventArgs e)
{
    // If the request was not canceled and did not throw 
    // an exception, display the resource. 
    if (!e.Cancelled && e.Error == null)
    {
        string textString = (string)e.Result;

        Console.WriteLine (textString);
    }
}

查看 MSDN 网站上的 WebClient.DownloadStringAsync Method 和 WebClient.DownloadFileAsync Method 页面了解更多信息。

Answer 2

您不能在后台线程上创建 UI 控件，在这种情况下您不需要这样做，因为无论如何您需要的所有 WebBrowser 方法都是异步执行的...

WebBrowser.Navigate

异步导航到指定 Uri 处的文档。

顺便说一句，在加载WebBrowser 控件后不要忘记使用Navigate 方法，因此请使用IsLoaded 检查或从Loaded 事件调用导航...

Answer 3

某些 UI 操作需要在 UI 线程上调用。试试看

    private void bgw_DoWork(object sender, DoWorkEventArgs e)
    {
        wb.Navigated += wb_Navigated;
        wb.LoadCompleted += wb_LoadCompleted;

        wb.Dispatcher.Invoke(() =>
        {

            wb.Navigate("http://www.google.com");
        });
    }