Download imagine con httpwebrequest

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Timer1.Enabled = True
    End Sub
    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick
        Timer1.Enabled = False
        ' Load the webpage into a WebBrowser control
        WebBrowser1.ScriptErrorsSuppressed = True
        WebBrowser1.Navigate("http://www.miosito.controlScreenShot")
    End Sub
    Private Sub WebBrowser1_DocumentCompleted(sender As System.Object, e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles webbrowser1.DocumentCompleted
        If Not WebBrowser1.Url.Equals("equals:blank") Then
            WebBrowser1.ScriptErrorsSuppressed = True
            WebBrowser1.Refresh()

        End If
        WebBrowser1.Width = Width
        webbrowser1.Height = Height
        If Width = -1 Then
            ' Take Screenshot of the web pages full width
            WebBrowser1.Width = WebBrowser1.Document.Body.ScrollRectangle.Width
        End If
        If Height = -1 Then
            ' Take Screenshot of the web pages full height
            webbrowser1.Height = webbrowser1.Document.Body.ScrollRectangle.Height
        End If
        Dim bitmap As New Bitmap(WebBrowser1.Width, WebBrowser1.Height)
        webbrowser1.DrawToBitmap(bitmap, New Rectangle(0, 0, webbrowser1.Width, webbrowser1.Height))
        PictureBox1.image = bitmap
        PictureBox1.Image.Save(TextBox2.Text, System.Drawing.Imaging.ImageFormat.Jpeg)

        Dim imag As New PictureBox()


        imag.Height = 200
        imag.Width = 370
        Dim myCallback As New Image.GetThumbnailImageAbort(AddressOf ThumbnailCallback)
        Dim myThumbnail As Image = bitmap.GetThumbnailImage(567, 330, myCallback, IntPtr.Zero)
        imag.Image = myThumbnail
        Flppictures.Controls.Add(imag)

    End Sub
    Public Function ThumbnailCallback() As Boolean
        Return False
    End Function