VB.NET 浏览器单击事件处理程序：'0' 的值对于'index'错误无效

Question

我尝试使用 VB.NET 制作一个小程序。

当它打开时，它会在网页下方显示一个网页和一个进程栏。当用户单击网页中的链接时，进度栏将停止处理并显示You clicked a link消息。处理完成后，它会显示另一条消息，内容为：Thanks for helping me 。

我在 VB.NET 中编写了整个过程的代码，但是当我调试它时，它会显示一条消息：

值"0"对"索引"无效。"索引"应介于 0 和 -1 之间。 参数名称：索引

我的代码是：

 Public Class MyPage
    Private Sub MyPage_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Timer1.Interval = 1500
    End Sub
    Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
        WebBrowser1.Document.Links(0).AttachEventHandler("onclick", AddressOf LinkClick)
    End Sub
    Sub LinkClick(ByVal sender As Object, ByVal e As System.EventArgs)
        Timer1.Start()
        MsgBox("You clicked the link", , "Clicked The link")
    End Sub
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        ProgressBar1.Increment(2)
        If ProgressBar1.Value = 100 Then
            Timer1.Stop()
            ProgressBar1.Value = 0
            MsgBox("Thanks for help me", , "Thankssss!")
        End If
    End Sub
 End Class

如何解决此问题？

Answer 1

你盲目地假设页面将始终有一个链接。 错误的假设。 修复：

Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
    If WebBrowser1.Document.Links.Count > 0 Then
        WebBrowser1.Document.Links(0).AttachEventHandler("onclick", AddressOf LinkClick)
    End If
End Sub

或者考虑到用法，越理智：

    For Each link As HtmlElement In WebBrowser1.Document.Links
        link.AttachEventHandler("onclick", AddressOf LinkClick)
    Next