c# - 在 WebBrowser 控件中修改 Javascript 变量

Question

我有一个网页，当访问该网页时，使用以下内容声明一个名为 date 的变量:

var date=new Date("03 Oct 2013 16:04:19");

然后该日期显示在页面顶部。我有办法修改那个日期变量吗？ (而不仅仅是可见的 HTML 源代码)

我一直在尝试使用 InvokeScript，但发现它很难掌握，如果有人知道并可以发布一些与此直接相关的示例，我将不胜感激。谢谢。

Answer 1

您可以使用 JavaScript 的 eval 注入(inject)任何 JavaScript 代码, 它适用于任何 IE 版本。您需要确保该页面至少有一个 <script>标记，但这很简单:

Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Call WebBrowser1.Navigate("http://example.com")
    End Sub

    Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
        '
        ' use WebBrowser1.Document.InvokeScript to inject script
        '
        ' make sure the page has at least one script element, so eval works
        WebBrowser1.Document.Body.AppendChild(WebBrowser1.Document.CreateElement("script"))
        WebBrowser1.Document.InvokeScript("eval", New [Object]() {"(function() { window.newDate=new Date('03 Oct 2013 16:04:19'); })()"})
        Dim result As String = WebBrowser1.Document.InvokeScript("eval", New [Object]() {"(function() { return window.newDate.toString(); })()"})
        MessageBox.Show(result)

    End Sub

End Class

或者，您可以使用VB.NET 后期绑定(bind)来调用eval直接，而不是 Document.InvokeScript ，这可能更容易编码和阅读:

Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Call WebBrowser1.Navigate("http://example.com")
    End Sub

    Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted

        '
        ' use VB late binding to call eval directly (seamlessly provided by.NET DLR)
        '
        Dim htmlDocument = WebBrowser1.Document.DomDocument
        Dim htmlWindow = htmlDocument.parentWindow
        ' make sure the page has at least one script element, so eval works
        htmlDocument.body.appendChild(htmlDocument.createElement("script"))
        htmlWindow.eval("var anotherDate = new Date('04 Oct 2013 16:04:19').toString()")
        MessageBox.Show(htmlWindow.anotherDate)
        ' the above shows we don't have to use JavaScript anonymous function,
        ' but it's always a good coding style to do so, to scope the context:
        htmlWindow.eval("window.createNewDate = function(){ return new Date().toString(); }")
        MessageBox.Show(htmlWindow.eval("window.createNewDate()"))

        ' we can also mix late binding and InvokeScript
        MessageBox.Show(WebBrowser1.Document.InvokeScript("createNewDate"))

    End Sub

End Class