Convert a Windows path to a URL

    Function ConvertWindowsPathToUrl(WindowsPathAndFilename As String) As String
        Dim ReturnValue As String = WindowsPathAndFilename
        'Make sure the file really exists.
        If My.Computer.FileSystem.FileExists(WindowsPathAndFilename) = True Then
            Dim WindowsFileInfo As IO.FileInfo = My.Computer.FileSystem.GetFileInfo(WindowsPathAndFilename)
            Dim WindowsFullFilename = WindowsFileInfo.FullName
            Dim ThisPageWindowsPath As String = Request.PhysicalPath
            Dim ThisPageFileInfo As IO.FileInfo = My.Computer.FileSystem.GetFileInfo(ThisPageWindowsPath)
            Dim ThisPageFolder As String = ThisPageFileInfo.Directory.FullName
            Dim ThisPageUrl As String = Page.ResolveClientUrl(Request.CurrentExecutionFilePath)
            Dim ThisPageUrlFolder As String = System.Web.VirtualPathUtility.GetDirectory(ThisPageUrl)
            If WindowsFullFilename.Contains(ThisPageFolder) = True Then
                'Only return a URL if the path to the file is the same as or under the path to this page.
                Dim UrlText As String = WindowsFullFilename
                UrlText = UrlText.Replace(ThisPageFolder & "\", ThisPageUrlFolder)
                UrlText = UrlText.Replace("\", "/")
                UrlText = System.Uri.EscapeUriString(UrlText)
                ReturnValue = UrlText
            End If
        End If
        Return ReturnValue
    End Function