Automation of Internet Explorer Using shdocvw.dll and mshtml.tlb – A Case Study

Introduction

Microsoft Internet Explorer comes with a fairly comprehensive, although sparsely documented, Object Model. If you've used the Web Browser control in Access, you are already familiar with the capabilities of IE's Object Model. All of the functionality in IE's object model (not counting external support, like scripting support etc.) is provided by the following two DLLs:

    shdocvw.dll (Microsoft Internet Controls)
    mshtml.tlb (Microsoft HTML Object Library)

You can automate IE to save an HTML file locally, inspect all the elements, and parse out a particular item at runtime.

Here's some sample code that automates through Internet Explorer Windows login into rediffmail.com, if the user name and password are valid.

First, the application opens the http://rediff.com site. It types the user name and password at the specified location and clicks the Submit button so that it goes to the Inbox page. It also opens the Compose page for the particular user.

The application extensively uses the shdocvw.InternetExplorer object and the mshtml.Document object.

Private Sub Form1_Load(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles MyBase.Load
    Dim wbBrowser As New SHDocVw.InternetExplorer wbBrowser.Visible = True
    wbBrowser.Navigate("http://www.rediff.com", Nothing, Nothing, Nothing, Nothing)
    Do
    Loop Until Not wbBrowser.Busy
    LoginIntoSite(wbBrowser)
    OpennComposePage(wbBrowser)
End Sub

Public Sub LoginIntoSite(ByRef wbBrowser As SHDocVw.InternetExplorer)

    Dim HTMLDoc As mshtml.HTMLDocument

    Do
    Loop Until Not wbBrowser.Busy

    HTMLDoc = wbBrowser.Document

    Dim iHTMLCol As IHTMLElementCollection
    Dim iHTMLEle As IHTMLElement
    Dim str, userName, passwd As String
   
    iHTMLCol = HTMLDoc.getElementsByTagName("input")
   
    ' Type the user name in the username text box
    For Each iHTMLEle In iHTMLCol
        If Not iHTMLEle.getAttribute("name") Is Nothing Then
            str = iHTMLEle.getAttribute("name").ToString
            If str = "login" Then
                iHTMLEle.setAttribute("value", "<VALID USER NAME>")
                Exit For
            End If
        End If
    Next

Read more: Codeproject
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