Why does backgroundworker lags or freezes for a bit when waiting for page to load on webbrowser?

问题

I'm running a backgroundworker for my webbrowser on a winform, it works and all, but why does the UI lags or freezes for a moment to wait for the page to load when I want it to load in the background so that the UI is fully functional?

Private Property pageready As Boolean = False

Public Sub WaitForPageLoad()
    AddHandler WebBrowser1.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf PageWaiter)
    While Not pageready
        Application.DoEvents()
    End While
    pageready = False
End Sub

Public Sub PageWaiter(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs)
    If WebBrowser1.ReadyState = WebBrowserReadyState.Complete Then
        pageready = True
        RemoveHandler WebBrowser1.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf PageWaiter)
    End If
End Sub

Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    Try
        WebBrowser1.Navigate("http://www.mypage.com")
        WaitForPageLoad() >>>> Lags and freezes UI for a sec or two to wait for page loading. How can i do this in the background?
    Catch ex As Exception
    End Try
End Sub

Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
    'Here i will get my attributes off the webpage ect....
End Sub

来源：https://stackoverflow.com/questions/39515807/why-does-backgroundworker-lags-or-freezes-for-a-bit-when-waiting-for-page-to-loa