加载Ajax后获取WebBrowser1 html内容(Vb2010)

在VB2010中加载Ajax后获取WebBrowser控件HTML内容

基础概念

在VB2010中使用WebBrowser控件时，当页面包含Ajax异步加载内容时，直接获取Document属性可能无法获取完整内容，因为Ajax是异步加载的。

解决方案

方法一：等待页面完全加载

Private Sub WebBrowser1_DocumentCompleted(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
    ' 确保是所有框架都加载完成
    If WebBrowser1.ReadyState = WebBrowserReadyState.Complete Then
        ' 获取完整的HTML内容
        Dim htmlContent As String = WebBrowser1.Document.Body.OuterHtml
        ' 或者获取整个文档
        ' Dim htmlContent As String = WebBrowser1.Document.DocumentElement.OuterHtml
        
        ' 在这里处理获取到的HTML内容
        MessageBox.Show("页面加载完成，HTML内容已获取")
    End If
End Sub

方法二：使用定时器检查Ajax加载完成

' 添加一个Timer控件Timer1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    WebBrowser1.Navigate("http://example.com")
    Timer1.Interval = 1000 ' 1秒检查一次
    Timer1.Start()
End Sub

Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
    ' 检查特定元素是否存在或内容是否变化
    If WebBrowser1.Document IsNot Nothing AndAlso WebBrowser1.Document.Body IsNot Nothing Then
        Dim element = WebBrowser1.Document.GetElementById("ajaxContent")
        If element IsNot Nothing AndAlso element.InnerHtml.Contains("expected content") Then
            Timer1.Stop()
            Dim htmlContent As String = WebBrowser1.Document.Body.OuterHtml
            ' 处理获取到的HTML内容
        End If
    End If
End Sub

方法三：注入JavaScript监听Ajax完成

Private Sub WebBrowser1_DocumentCompleted(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
    If WebBrowser1.ReadyState = WebBrowserReadyState.Complete Then
        ' 注入JavaScript来监听Ajax请求完成
        Dim head As HtmlElement = WebBrowser1.Document.GetElementsByTagName("head")(0)
        Dim scriptEl As HtmlElement = WebBrowser1.Document.CreateElement("script")
        Dim element As IHTMLScriptElement = DirectCast(scriptEl.DomElement, IHTMLScriptElement)
        element.text = "
            var oldXHROpen = window.XMLHttpRequest.prototype.open;
            window.XMLHttpRequest.prototype.open = function(method, url, async, user, password) {
                this.addEventListener('load', function() {
                    window.external.AjaxComplete();
                });
                return oldXHROpen.apply(this, arguments);
            }
        "
        head.AppendChild(scriptEl)
    End If
End Sub

' 需要在类中添加以下代码
<System.Runtime.InteropServices.ComVisibleAttribute(True)>
Public Class ExternalMethods
    Public Sub AjaxComplete()
        ' Ajax请求完成时调用
        Dim htmlContent As String = WebBrowser1.Document.Body.OuterHtml
        ' 处理获取到的HTML内容
    End Sub
End Class

' 在Form_Load中设置
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    WebBrowser1.ObjectForScripting = New ExternalMethods()
End Sub