C#WPF - 等待加载页面

Question

我在StackOverflow上看到了关于这个主题的几个主题,但是它们似乎都没有提供答案.

我有一个按钮,当点击它时,会打开一个不可见的网页,导航到一个URL,将信息输入一个框,按一个按钮,然后抓取屏幕以获取信息.

我的代码的骨头基本上在点击中:

WebBrowser wb = new WebBrowser;
wb.Visibility = System.Windows.Visibility.Hidden;
wb.Navigate("http://somepage.com");

这就是它变得棘手的地方.

我正在寻找一种方法来确保在尝试输入数据或刮擦屏幕之前加载页面.我见过几个线程谈Navigated,IsLoaded,LoadCompleted以及BackgroundWork东西,但我不能让任何这些工作.

哪个是用于确定页面已完全加载的最佳选项？您如何获得所选择的方法？

我也无法从屏幕上获取数据,因为WPF不使用相同的数据GetElementByID.

编辑:

根据下面的评论,这里是我遇到的错误:

• 一旦页面被导航,首先导航,并且不一定等到所有对象都被加载.这可以按预期工作,但不能用于我的目的.

• IsLoaded 永远不会回归真实

  private void GetData_Click(object sender, RoutedEventArgs e)
  {
    int x=0;
    HTMLDocument doc;
  
    wb = new WebBrowser();
    wb.Visibility = System.Windows.Visibility.Visible;
    wb.Navigate("somesite.com");
  
    doc = wb.Document as mshtml.HTMLDocument;
  
    while(!wb.IsLoaded)
    {
      //Wait
    }
  
    doc.getElementById("txt_One").innerText = "It Worked";
  
  }
  

将它置于无限循环中,wb似乎无法加载.

• 这是LoadCompleted的版本

事件'System.Windows.Controls.WebBrowser.LoadCompleted'只能出现在+ =或 - =的左侧

    private void GetData_Click(object sender, RoutedEventArgs e)
    {
      int x=0;
      HTMLDocument doc;

      wb = new WebBrowser();
      wb.Visibility = System.Windows.Visibility.Visible;
      wb.Navigate("somesite.com");

      doc = wb.Document as mshtml.HTMLDocument;

      wb.LoadCompleted += wb_LoadCompleted;

      doc.getElementById("txt_One").innerText = "It Worked";

    }

    void wb_LoadCompleted(object sender, NavigationEventArgs e)
    {

    }

产生错误

{filename}中出现未处理的"System.NullReferenceException"类型异常

附加信息:未将对象引用设置为对象的实例.

Answer 1

webbrowser控件有一个loadedevent(你有):LoadCompleted:当dom完全加载时触发.

绑定事件并在事件方法中获取文档而不是立即.

    //root is a grid element identified in the XAML
    public WebBrowser webb;

    public MainWindow()
    {
        InitializeComponent();

        webb = new WebBrowser();
        webb.Visibility = System.Windows.Visibility.Hidden;
        root.Children.Add(webb);
        webb.LoadCompleted += webb_LoadCompleted;
        webb.Navigate("http://www.google.com");
    }

    void webb_LoadCompleted(object sender, NavigationEventArgs e)
    {
        MessageBox.Show("Completed loading the page");

        mshtml.HTMLDocument doc = webb.Document as mshtml.HTMLDocument;
        mshtml.HTMLInputElement obj = doc.getElementById("gs_taif0") as mshtml.HTMLInputElement;
        mshtml.HTMLFormElement form = doc.forms.item(Type.Missing, 0) as mshtml.HTMLFormElement;

        webb.LoadCompleted -= webb_LoadCompleted; //REMOVE THE OLD EVENT METHOD BINDING
        webb.LoadCompleted += webb_LoadCompleted2; //BIND TO A NEW METHOD FOR THE EVENT
        obj.value = "test search";
        form.submit(); //PERFORM THE POST ON THE FORM OR SEARCH
    }

    //SECOND EVENT TO FIRE AFTER YOU POST INFORMATION
    void webb_LoadCompleted2(object sender, NavigationEventArgs e)
    {
        MessageBox.Show("Completed loading the page second time after post"); 
    }

您需要将doc = wb.Document作为mshtml.HTMLDocument; 在loadcompleted事件中.因为在加载完成之前,您无法获取文档.