How to wait until WebBrowser is completely loaded in VB.NET?

Question

I am using the WebBrowser control in my VB.NET application to load a few URLs ( ~10-15) and save their HTML source in a text file. However, my code doesn't write the source of the current page rather the initial one because the it is triggered even before the page is loaded.

How can I wait until the page is completely loaded before calling any event?

I tried the following code but it doesn't work.

Do Until WebBrowser1.ReadyState = WebBrowserReadyState.Complete
   Application.DoEvents()
Loop

Answer 1

Salvete! I needed, simply, a function I could call to make the code wait for the page to load before it continued. After scouring the web for answers, and fiddling around for several hours, I came up with this to solve for myself, the exact dilemma you present. I know I am late in the game with an answer, but I wish to post this for anyone else who comes along.

usage: just call WaitForPageLoad() just after a call to navigation:

whatbrowser.Navigate("http://www.google.com")
WaitForPageLoad()

another example we don't combine the navigate feature with the page load, because sometimes you need to wait for a load without also navigating, for example, you might need to wait for a page to load that was started with an invokemember event:

whatbrowser.Document.GetElementById("UserName").InnerText = whatusername
whatbrowser.Document.GetElementById("Password").InnerText = whatpassword
whatbrowser.Document.GetElementById("LoginButton").InvokeMember("click")
WaitForPageLoad()

Here is the code: You need both subs plus the accessible variable, pageready. First, make sure to fix the variable called whatbrowser to be your webbrowser control

Now, somewhere in your module or class, place this:

Private Property pageready As Boolean = False

#Region "Page Loading Functions"
    Private Sub WaitForPageLoad()
        AddHandler whatbrowser.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf PageWaiter)
        While Not pageready
            Application.DoEvents()
        End While
        pageready = False
    End Sub

    Private Sub PageWaiter(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs)
        If whatbrowser.ReadyState = WebBrowserReadyState.Complete Then
            pageready = True
            RemoveHandler whatbrowser.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf PageWaiter)
        End If
    End Sub

#End Region

Answer 2

Sounds like you want to catch the DocumentCompleted event of your webbrowser control.

MSDN has a couple of good articles about the webbrowser control - WebBrowser Class has lots of examples, and How to: Add Web Browser Capabilities to a Windows Forms Application

Answer 3

Technically, there are two issues with the code posted by BGM:

1. the adding of the handlers in the WaitForPageLoad method is potentially too late. The navigation is initiated before the handlers are added which means that in very rare cases where the browser already has the page it may complete before the handlers are added in which case you will miss the event and sit forever waiting.

   The solution is to add the handlers before the navigation starts and remove them after the navigation completed

   This means the WaitForPageLoad method needs to be split into two methods. One is called before initiating the navigation. It should set the handlers. The second part does the ReadyState monitoring and cleans up when 'Ready'.

2. good programming practices is to add a timeout so that a lost (or crashed, or looping) browser doesn't make your code wait forever for the document completed even