C#：“如何使用 WebBrowser 并将 html 打印到控制台。”

Question

我已经花了超过 10 个小时试图找到一个通向 WebBrowser 属性的洞。

我只是想导航到 google.com 并将 html 代码打印到控制台。这不断给我一个空参考。

有很多与此相关的问题，他们都说需要 DocumentCompleted 事件处理程序或未正确设置。

所以我尽我所能尝试了这个，但仍然没有运气。然后我甚至从Microsoft复制粘贴官方示例我仍然得到空引用！

    using System;
    using System.Windows.Forms;


    namespace Aamanss
    {
        class MainClass
        {
            public static void PrintHelpPage()
            {
                // Create a WebBrowser instance. 
                WebBrowser webBrowserForPrinting = new WebBrowser();

                // Add an event handler that prints the document after it loads.
                webBrowserForPrinting.DocumentCompleted +=
                    new WebBrowserDocumentCompletedEventHandler(PrintDocument);

                // Set the Url property to load the document.
                webBrowserForPrinting.Url = new Uri("https://www.google.com");
            }

            public static void PrintDocument(object sender,
                WebBrowserDocumentCompletedEventArgs e)
            {
                // Print the document now that it is fully loaded.
                ((WebBrowser)sender).Print();

                // Dispose the WebBrowser now that the task is complete. 
                ((WebBrowser)sender).Dispose();
            }

            public static void Main(string[] args)
            {
                PrintHelpPage();
            }
        }

}

如您所见，上面的大部分代码都是从 Microsoft 复制粘贴的。这个错误：

Gtk-Message: Failed to load module "atk-bridge"
libgluezilla not found. To have webbrowser support, you need libgluezilla installed        
System.NullReferenceException: Object reference not set to an instance of an object
      at System.Windows.Forms.WebBrowser.Navigate (System.Uri url) [0x0000e] in /run/build/mono/mcs/class/System.Windows.Forms/System.Windows.Forms/WebBrowser.cs:304 
      at System.Windows.Forms.WebBrowser.set_Url (System.Uri value) [0x00007] in /run/build/mono/mcs/class/System.Windows.Forms/System.Windows.Forms/WebBrowser.cs:231 
      at (wrapper remoting-invoke-with-check) System.Windows.Forms.WebBrowser:set_Url (System.Uri)
      at Aamanss.MainClass.PrintHelpPage () [0x00024] in /root/Projects/Aamanss/Aamanss/Program.cs:19 
      at Aamanss.MainClass.Main (System.String[] args) [0x00001] in /root/Projects/Aamanss/Aamanss/Program.cs:34 
    [ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
      at System.Windows.Forms.WebBrowser.Navigate (System.Uri url) [0x0000e] in /run/build/mono/mcs/class/System.Windows.Forms/System.Windows.Forms/WebBrowser.cs:304 
      at System.Windows.Forms.WebBrowser.set_Url (System.Uri value) [0x00007] in /run/build/mono/mcs/class/System.Windows.Forms/System.Windows.Forms/WebBrowser.cs:231 
      at (wrapper remoting-invoke-with-check) System.Windows.Forms.WebBrowser:set_Url (System.Uri)
      at Aamanss.MainClass.PrintHelpPage () [0x00024] in /root/Projects/Aamanss/Aamanss/Program.cs:19 
      at Aamanss.MainClass.Main (System.String[] args) [0x00001] in /root/Projects/Aamanss/Aamanss/Program.cs:34

我真的很想弄清楚您是如何使 WebBrowser Navigation 正常工作的，因此我真诚地希望你们中的某个人可以为傻瓜说明这一点。

Answer 1

好的，

我误解了它是一个Windows应用程序（Winforms）的问题

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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            PrintHelpPage();
            Console.ReadKey();
        }

        public static void PrintHelpPage()
        {
            var th = new Thread(() => {
                var br = new WebBrowser();
                br.DocumentCompleted += PrintDocument;
                br.Navigate("http://google.com");
                Application.Run();
            });
            th.SetApartmentState(ApartmentState.STA);
            th.Start();
        }

        public static void PrintDocument(object sender,
            WebBrowserDocumentCompletedEventArgs e)
        {
            var browser = sender as WebBrowser;
            // Print the document now that it is fully loaded.
            browser.Print();

            // Dispose the WebBrowser now that the task is complete. 
            browser.Dispose();
        }
    }
}

问题是控制台应用程序不会触发 DocumentCompletedEvent，除非您像我在线程中那样明确标记它 STAThread。