Question

我希望标题足够清晰，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WebBrowser控件并尝试使用wb.DocumentText设置内容。但是当我尝试遍历元素时，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包含HTML简报消息，其中有一些标记。

我已经尝试过这个：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。 {@ 3}}网页抓取，使用async/await来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);
                }
            }
        }
    }
}

Answer 2

您需要在触发事件webBrowser1_DocumentCompleted后循环元素。因此您需要在代码中使用它

webBrowser1.DocumentCompleted+=new WebBrowserDocumentCompletedEventHandler(webBrowser1_DocumentCompleted);

private void webBrowser1_DocumentCompleted(object sender,WebBrowserDocumentCompletedEventArgs e)
{
   //here you can to loop your elements     
}

Answer 3

试试这个：

WebBrowser wb;
private void Form1_Load(object sender, EventArgs e)
{
    wb = new WebBrowser();
    wb.DocumentCompleted += wb_DocumentCompleted;
    wb.DocumentText = "<html><body><a href='#'>Test</a></body></html>";
}

void wb_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
    HtmlElementCollection elems = ((WebBrowser)sender)
        .Document.GetElementsByTagName("a");
    foreach (HtmlElement elem in elems)
    {
        // Do Some Stuff
    }
}

C＃使用webbrowser documenttext，文档保持为null

3 个答案: