C#使用webbrowser documenttext,文档保持为null

Question

我希望标题足够清楚,但我会尝试解释......

我正在使用C#Winforms(dotnet 4.5).

问题是我正在创建一个WebBrowser控件并尝试设置内容wb.DocumentText.但是当我尝试循环遍历元素时,它表示文档为空(null)

这是我的代码:

WebBrowser wb = new WebBrowser();
wb.DocumentText = leMessage;

HtmlElementCollection elems = wb.Document.GetElementsByTagName("a");
foreach (HtmlElement elem in elems)
{
    // Do Some Stuff
}

leMessage 持有HTML简报消息,其中有一些标签.

我已经尝试了这个:wb.Document.Body.InnerHtml = leMessage;但是这也不起作用......

我错过了什么或做错了什么？

Answer 1

WebBrowser.DocumentText是异步的.您需要先处理DocumentComplete才能访问DOM,并继续处理Windows消息.这是一个完整的网络报废示例,async/await用于保持方便的线性代码流.只需改变导航部分:

await NavigateAsync(ct, () => this.webBrowser.DocumentText = leMessage), timeout);
HtmlElementCollection elems = wb.Document.GetElementsByTagName("a");

这样你就可以循环完成.简而言之:

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

namespace WinformsApp2
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        const string leMessage = "<a href='http://example.com'>Go there</a>";

        private async void MainForm_Load(object sender, EventArgs e)
        {
            var wb = new WebBrowser();

            TaskCompletionSource<bool> tcs = null;
            WebBrowserDocumentCompletedEventHandler documentCompletedHandler = (sender2, e2) => tcs.TrySetResult(true);

            for (int i = 0; i < 3; i++)
            {
                tcs = new TaskCompletionSource<bool>();
                wb.DocumentCompleted += documentCompletedHandler;
                try {
                    wb.DocumentText = leMessage;
                    await tcs.Task;
                }
                finally {
                    wb.DocumentCompleted -= documentCompletedHandler;
                }
                HtmlElementCollection elems = wb.Document.GetElementsByTagName("a");
                foreach (HtmlElement elem in elems)
                {
                    Debug.Print(elem.OuterHtml);
                }
            }
        }
    }
}